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Add solution 1654、1655

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YDZ
2020-11-28 15:24:45 +08:00
parent 0c4b373319
commit 9ac3fdeb96
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34
leetcode/1653.Minimum-Deletions-to-Make-String-Balanced/1653. Minimum Deletions to Make String Balanced_test.go
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@ -5,52 +5,52 @@ import (
"testing" "testing"
) )
type question1649 struct { type question1653 struct {
para1649 para1653
ans1649 ans1653
} }
// para 是参数 // para 是参数
// one 代表第一个参数 // one 代表第一个参数
type para1649 struct { type para1653 struct {
s string s string
} }
// ans 是答案 // ans 是答案
// one 代表第一个答案 // one 代表第一个答案
type ans1649 struct { type ans1653 struct {
one int one int
} }
func Test_Problem1649(t *testing.T) { func Test_Problem1653(t *testing.T) {
qs := []question1649{ qs := []question1653{
{ {
para1649{"aababbab"}, para1653{"aababbab"},
ans1649{2}, ans1653{2},
}, },
{ {
para1649{"bbaaaaabb"}, para1653{"bbaaaaabb"},
ans1649{2}, ans1653{2},
}, },
{ {
para1649{"b"}, para1653{"b"},
ans1649{0}, ans1653{0},
}, },
{ {
para1649{"ababaaaabbbbbaaababbbbbbaaabbaababbabbbbaabbbbaabbabbabaabbbababaa"}, para1653{"ababaaaabbbbbaaababbbbbbaaabbaababbabbbbaabbbbaabbabbabaabbbababaa"},
ans1649{25}, ans1653{25},
}, },
} }
fmt.Printf("------------------------Leetcode Problem 1649------------------------\n") fmt.Printf("------------------------Leetcode Problem 1653------------------------\n")
for _, q := range qs { for _, q := range qs {
_, p := q.ans1649, q.para1649 _, p := q.ans1653, q.para1653
fmt.Printf("【input】:%v 【output】:%v \n", p, minimumDeletions(p.s)) fmt.Printf("【input】:%v 【output】:%v \n", p, minimumDeletions(p.s))
} }
fmt.Printf("\n\n\n") fmt.Printf("\n\n\n")

29
leetcode/1654.Minimum-Jumps-to-Reach-Home/1654. Minimum Jumps to Reach Home.go Normal file
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@ -0,0 +1,29 @@
package leetcode
func minimumJumps(forbidden []int, a int, b int, x int) int {
visited := make([]bool, 6000)
for i := range forbidden {
visited[forbidden[i]] = true
}
queue, res := [][2]int{{0, 0}}, -1
for len(queue) > 0 {
length := len(queue)
res++
for i := 0; i < length; i++ {
cur, isBack := queue[i][0], queue[i][1]
if cur == x {
return res
}
if isBack == 0 && cur-b > 0 && !visited[cur-b] {
visited[cur-b] = true
queue = append(queue, [2]int{cur - b, 1})
}
if cur+a < len(visited) && !visited[cur+a] {
visited[cur+a] = true
queue = append(queue, [2]int{cur + a, 0})
}
}
queue = queue[length:]
}
return -1
}

60
leetcode/1654.Minimum-Jumps-to-Reach-Home/1654. Minimum Jumps to Reach Home_test.go Normal file
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@ -0,0 +1,60 @@
package leetcode
import (
"fmt"
"testing"
)
type question1654 struct {
para1654
ans1654
}
// para 是参数
// one 代表第一个参数
type para1654 struct {
forbidden []int
a int
b int
x int
}
// ans 是答案
// one 代表第一个答案
type ans1654 struct {
one int
}
func Test_Problem1654(t *testing.T) {
qs := []question1654{
{
para1654{[]int{14, 4, 18, 1, 15}, 3, 15, 9},
ans1654{3},
},
{
para1654{[]int{8, 3, 16, 6, 12, 20}, 15, 13, 11},
ans1654{-1},
},
{
para1654{[]int{1, 6, 2, 14, 5, 17, 4}, 16, 9, 7},
ans1654{2},
},
{
para1654{[]int{1998}, 1999, 2000, 2000},
ans1654{3998},
},
}
fmt.Printf("------------------------Leetcode Problem 1654------------------------\n")
for _, q := range qs {
_, p := q.ans1654, q.para1654
fmt.Printf("【input】:%v 【output】:%v \n", p, minimumJumps(p.forbidden, p.a, p.b, p.x))
}
fmt.Printf("\n\n\n")
}

101
leetcode/1654.Minimum-Jumps-to-Reach-Home/README.md Normal file
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@ -0,0 +1,101 @@
# [1654. Minimum Jumps to Reach Home](https://leetcode.com/problems/minimum-jumps-to-reach-home/)
## 题目
A certain bug's home is on the x-axis at position `x`. Help them get there from position `0`.
The bug jumps according to the following rules:
- It can jump exactly `a` positions **forward** (to the right).
- It can jump exactly `b` positions **backward** (to the left).
- It cannot jump backward twice in a row.
- It cannot jump to any `forbidden` positions.
The bug may jump forward **beyond** its home, but it **cannot jump** to positions numbered with **negative** integers.
Given an array of integers `forbidden`, where `forbidden[i]` means that the bug cannot jump to the position `forbidden[i]`, and integers `a`, `b`, and `x`, return *the minimum number of jumps needed for the bug to reach its home*. If there is no possible sequence of jumps that lands the bug on position `x`, return `1.`
**Example 1:**
```
Input: forbidden = [14,4,18,1,15], a = 3, b = 15, x = 9
Output: 3
Explanation: 3 jumps forward (0 -> 3 -> 6 -> 9) will get the bug home.
```
**Example 2:**
```
Input: forbidden = [8,3,16,6,12,20], a = 15, b = 13, x = 11
Output: -1
```
**Example 3:**
```
Input: forbidden = [1,6,2,14,5,17,4], a = 16, b = 9, x = 7
Output: 2
Explanation: One jump forward (0 -> 16) then one jump backward (16 -> 7) will get the bug home.
```
**Constraints:**
- `1 <= forbidden.length <= 1000`
- `1 <= a, b, forbidden[i] <= 2000`
- `0 <= x <= 2000`
- All the elements in `forbidden` are distinct.
- Position `x` is not forbidden.
## 题目大意
有一只跳蚤的家在数轴上的位置 x 处。请你帮助它从位置 0 出发，到达它的家。
跳蚤跳跃的规则如下：
- 它可以 往前 跳恰好 a 个位置（即往右跳）。
- 它可以 往后 跳恰好 b 个位置（即往左跳）。
- 它不能 连续 往后跳 2 次。
- 它不能跳到任何 forbidden 数组中的位置。
跳蚤可以往前跳 超过 它的家的位置，但是它 不能跳到负整数 的位置。给你一个整数数组 forbidden ，其中 forbidden[i] 是跳蚤不能跳到的位置，同时给你整数 a， b 和 x ，请你返回跳蚤到家的最少跳跃次数。如果没有恰好到达 x 的可行方案，请你返回 -1 。
## 解题思路
- 给出坐标 x ，可以往前跳的步长 a，往后跳的步长 b。要求输出能跳回家的最少跳跃次数。
- 求最少跳跃次数，思路用 BFS 求解，最先到达坐标 x 的方案即是最少跳跃次数。对`forbidden` 的处理是把记忆化数组里面把他们标记为 true。禁止连续往后跳 2 次的限制，要求我们在 BFS 入队的时候再记录一下跳跃方向，每次往后跳的时候判断前一跳是否是往后跳，如果是往后跳，此次就不能往后跳了。
## 代码
```go
package leetcode
func minimumJumps(forbidden []int, a int, b int, x int) int {
visited := make([]bool, 6000)
for i := range forbidden {
visited[forbidden[i]] = true
}
queue, res := [][2]int{{0, 0}}, -1
for len(queue) > 0 {
length := len(queue)
res++
for i := 0; i < length; i++ {
cur, isBack := queue[i][0], queue[i][1]
if cur == x {
return res
}
if isBack == 0 && cur-b > 0 && !visited[cur-b] {
visited[cur-b] = true
queue = append(queue, [2]int{cur - b, 1})
}
if cur+a < len(visited) && !visited[cur+a] {
visited[cur+a] = true
queue = append(queue, [2]int{cur + a, 0})
}
}
queue = queue[length:]
}
return -1
}
```

30
leetcode/1655.Distribute-Repeating-Integers/1655. Distribute Repeating Integers.go Normal file
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@ -0,0 +1,30 @@
package leetcode
func canDistribute(nums []int, quantity []int) bool {
freq := make(map[int]int)
for _, n := range nums {
freq[n]++
}
return dfs(freq, quantity)
}
func dfs(freq map[int]int, quantity []int) bool {
if len(quantity) == 0 {
return true
}
visited := make(map[int]bool)
for i := range freq {
if visited[freq[i]] {
continue
}
visited[freq[i]] = true
if freq[i] >= quantity[0] {
freq[i] -= quantity[0]
if dfs(freq, quantity[1:]) {
return true
}
freq[i] += quantity[0]
}
}
return false
}

63
leetcode/1655.Distribute-Repeating-Integers/1655. Distribute Repeating Integers_test.go Normal file
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@ -0,0 +1,63 @@
package leetcode
import (
"fmt"
"testing"
)
type question1655 struct {
para1655
ans1655
}
// para 是参数
// one 代表第一个参数
type para1655 struct {
nums []int
quantity []int
}
// ans 是答案
// one 代表第一个答案
type ans1655 struct {
one bool
}
func Test_Problem1655(t *testing.T) {
qs := []question1655{
{
para1655{[]int{1, 2, 3, 4}, []int{2}},
ans1655{false},
},
{
para1655{[]int{1, 2, 3, 3}, []int{2}},
ans1655{true},
},
{
para1655{[]int{1, 1, 2, 2}, []int{2, 2}},
ans1655{true},
},
{
para1655{[]int{1, 1, 2, 3}, []int{2, 2}},
ans1655{false},
},
{
para1655{[]int{1, 1, 1, 1, 1}, []int{2, 3}},
ans1655{true},
},
}
fmt.Printf("------------------------Leetcode Problem 1655------------------------\n")
for _, q := range qs {
_, p := q.ans1655, q.para1655
fmt.Printf("【input】:%v 【output】:%v \n", p, canDistribute(p.nums, p.quantity))
}
fmt.Printf("\n\n\n")
}

112
leetcode/1655.Distribute-Repeating-Integers/README.md Normal file
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@ -0,0 +1,112 @@
# [1655. Distribute Repeating Integers](https://leetcode.com/problems/distribute-repeating-integers/)
## 题目
You are given an array of `n` integers, `nums`, where there are at most `50` unique values in the array. You are also given an array of `m` customer order quantities, `quantity`, where `quantity[i]` is the amount of integers the `ith` customer ordered. Determine if it is possible to distribute `nums` such that:
- The `ith` customer gets **exactly** `quantity[i]` integers,
- The integers the `ith` customer gets are **all equal**, and
- Every customer is satisfied.
Return `true` *if it is possible to distribute* `nums` *according to the above conditions*.
**Example 1:**
```
Input: nums = [1,2,3,4], quantity = [2]
Output: false
Explanation: The 0th customer cannot be given two different integers.
```
**Example 2:**
```
Input: nums = [1,2,3,3], quantity = [2]
Output: true
Explanation: The 0th customer is given [3,3]. The integers [1,2] are not used.
```
**Example 3:**
```
Input: nums = [1,1,2,2], quantity = [2,2]
Output: true
Explanation: The 0th customer is given [1,1], and the 1st customer is given [2,2].
```
**Example 4:**
```
Input: nums = [1,1,2,3], quantity = [2,2]
Output: false
Explanation: Although the 0th customer could be given [1,1], the 1st customer cannot be satisfied.
```
**Example 5:**
```
Input: nums = [1,1,1,1,1], quantity = [2,3]
Output: true
Explanation: The 0th customer is given [1,1], and the 1st customer is given [1,1,1].
```
**Constraints:**
- `n == nums.length`
- `1 <= n <= 105`
- `1 <= nums[i] <= 1000`
- `m == quantity.length`
- `1 <= m <= 10`
- `1 <= quantity[i] <= 105`
- There are at most `50` unique values in `nums`.
## 题目大意
给你一个长度为 n 的整数数组 nums ，这个数组中至多有 50 个不同的值。同时你有 m 个顾客的订单 quantity ，其中，整数 quantity[i] 是第 i 位顾客订单的数目。请你判断是否能将 nums 中的整数分配给这些顾客，且满足：
- 第 i 位顾客 恰好 有 quantity[i] 个整数。
- 第 i 位顾客拿到的整数都是 相同的 。
- 每位顾客都满足上述两个要求。
如果你可以分配 nums 中的整数满足上面的要求，那么请返回 true ，否则返回 false 。
## 解题思路
- 给定一个数组 nums，订单数组 quantity，要求按照订单满足顾客的需求。如果能满足输出 true，不能满足输出 false。
- 用 DFS 记忆化暴力搜索。代码实现不难。（不知道此题为什么是 Hard）
## 代码
```go
package leetcode
func canDistribute(nums []int, quantity []int) bool {
freq := make(map[int]int)
for _, n := range nums {
freq[n]++
}
return dfs(freq, quantity)
}
func dfs(freq map[int]int, quantity []int) bool {
if len(quantity) == 0 {
return true
}
visited := make(map[int]bool)
for i := range freq {
if visited[freq[i]] {
continue
}
visited[freq[i]] = true
if freq[i] >= quantity[0] {
freq[i] -= quantity[0]
if dfs(freq, quantity[1:]) {
return true
}
freq[i] += quantity[0]
}
}
return false
}
```

56
leetcode/5550/1652. Defuse the Bomb.go
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@ -1,56 +0,0 @@
package leetcode
func decrypt(code []int, k int) []int {
if k == 0 {
for i := 0; i < len(code); i++ {
code[i] = 0
}
return code
}
count, sum, res := k, 0, make([]int, len(code))
if k > 0 {
for i := 0; i < len(code); i++ {
for j := i + 1; j < len(code); j++ {
if count == 0 {
break
}
sum += code[j]
count--
}
if count > 0 {
for j := 0; j < len(code); j++ {
if count == 0 {
break
}
sum += code[j]
count--
}
}
res[i] = sum
sum, count = 0, k
}
}
if k < 0 {
for i := 0; i < len(code); i++ {
for j := i - 1; j >= 0; j-- {
if count == 0 {
break
}
sum += code[j]
count++
}
if count < 0 {
for j := len(code) - 1; j >= 0; j-- {
if count == 0 {
break
}
sum += code[j]
count++
}
}
res[i] = sum
sum, count = 0, k
}
}
return res
}

53
leetcode/5550/1652. Defuse the Bomb_test.go
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@ -1,53 +0,0 @@
package leetcode
import (
"fmt"
"testing"
)
type question1652 struct {
para1652
ans1652
}
// para 是参数
// one 代表第一个参数
type para1652 struct {
code []int
k int
}
// ans 是答案
// one 代表第一个答案
type ans1652 struct {
one []int
}
func Test_Problem1652(t *testing.T) {
qs := []question1652{
{
para1652{[]int{5, 7, 1, 4}, 3},
ans1652{[]int{12, 10, 16, 13}},
},
{
para1652{[]int{1, 2, 3, 4}, 0},
ans1652{[]int{0, 0, 0, 0}},
},
{
para1652{[]int{2, 4, 9, 3}, -2},
ans1652{[]int{12, 5, 6, 13}},
},
}
fmt.Printf("------------------------Leetcode Problem 1652------------------------\n")
for _, q := range qs {
_, p := q.ans1652, q.para1652
fmt.Printf("【input】:%v 【output】:%v \n", p, decrypt(p.code, p.k))
}
fmt.Printf("\n\n\n")
}

49
leetcode/5551/5551. Minimum Deletions to Make String Balanced.go
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@ -1,49 +0,0 @@
package leetcode
func minimumDeletions(s string) int {
ai, bi, sum, temp, array := 0, 0, 0, 0, []int{}
for ai = 0; ai < len(s); ai++ {
if s[ai] == 'a' {
break
}
}
if ai != 0 && ai != len(s) {
sum += ai
}
for bi = ai; bi < len(s); bi++ {
if s[bi] == 'b' {
break
}
}
if s[bi-1] == 'a' {
ai = bi - 1
}
if s[bi-1] == 'b' && bi != len(s) {
ai = bi + 1
}
for j := bi; j < len(s); j++ {
if s[j] == 'b' {
temp++
}
if s[j] == 'a' && temp != 0 {
array = append(array, temp)
temp = 0
}
}
if len(array) == 0 {
return sum
}
dp := make([]int, len(array))
dp[0] = min(array[0], len(array))
for i := 1; i < len(array); i++ {
dp[i] = min(dp[i-1]+array[i], dp[i-1]+len(array)-(i+1)+1)
}
return sum + dp[len(array)-1]
}
func min(a int, b int) int {
if a > b {
return b
}
return a
}

57
leetcode/5551/5551. Minimum Deletions to Make String Balanced_test.go
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@ -1,57 +0,0 @@
package leetcode
import (
"fmt"
"testing"
)
type question1649 struct {
para1649
ans1649
}
// para 是参数
// one 代表第一个参数
type para1649 struct {
s string
}
// ans 是答案
// one 代表第一个答案
type ans1649 struct {
one int
}
func Test_Problem1649(t *testing.T) {
qs := []question1649{
// {
// para1649{"aababbab"},
// ans1649{2},
// },
// {
// para1649{"bbaaaaabb"},
// ans1649{2},
// },
{
para1649{"b"},
ans1649{0},
},
{
para1649{"ababaaaabbbbbaaababbbbbbaaabbaababbabbbbaabbbbaabbabbabaabbbababaa"},
ans1649{25},
},
}
fmt.Printf("------------------------Leetcode Problem 1649------------------------\n")
for _, q := range qs {
_, p := q.ans1649, q.para1649
fmt.Printf("【input】:%v 【output】:%v \n", p, minimumDeletions(p.s))
}
fmt.Printf("\n\n\n")
}

125
website/content/ChapterFour/1652.Defuse-the-Bomb.md Normal file
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@ -0,0 +1,125 @@
# [1652. Defuse the Bomb](https://leetcode.com/problems/defuse-the-bomb/)
## 题目
You have a bomb to defuse, and your time is running out! Your informer will provide you with a **circular** array `code` of length of `n` and a key `k`.
To decrypt the code, you must replace every number. All the numbers are replaced **simultaneously**.
- If `k > 0`, replace the `ith` number with the sum of the **next** `k` numbers.
- If `k < 0`, replace the `ith` number with the sum of the **previous** `k` numbers.
- If `k == 0`, replace the `ith` number with `0`.
As `code` is circular, the next element of `code[n-1]` is `code[0]`, and the previous element of `code[0]` is `code[n-1]`.
Given the **circular** array `code` and an integer key `k`, return *the decrypted code to defuse the bomb*!
**Example 1:**
```
Input: code = [5,7,1,4], k = 3
Output: [12,10,16,13]
Explanation: Each number is replaced by the sum of the next 3 numbers. The decrypted code is [7+1+4, 1+4+5, 4+5+7, 5+7+1]. Notice that the numbers wrap around.
```
**Example 2:**
```
Input: code = [1,2,3,4], k = 0
Output: [0,0,0,0]
Explanation: When k is zero, the numbers are replaced by 0.
```
**Example 3:**
```
Input: code = [2,4,9,3], k = -2
Output: [12,5,6,13]
Explanation: The decrypted code is [3+9, 2+3, 4+2, 9+4]. Notice that the numbers wrap around again. If k is negative, the sum is of the previous numbers.
```
**Constraints:**
- `n == code.length`
- `1 <= n <= 100`
- `1 <= code[i] <= 100`
- `(n - 1) <= k <= n - 1`
## 题目大意
你有一个炸弹需要拆除，时间紧迫！你的情报员会给你一个长度为 n 的 循环 数组 code 以及一个密钥 k 。为了获得正确的密码，你需要替换掉每一个数字。所有数字会 同时 被替换。
- 如果 k > 0 ，将第 i 个数字用 接下来 k 个数字之和替换。
- 如果 k < 0 ，将第 i 个数字用 之前 k 个数字之和替换。
- 如果 k == 0 ，将第 i 个数字用 0 替换。
由于 code 是循环的， code[n-1] 下一个元素是 code[0] ，且 code[0] 前一个元素是 code[n-1] 。
给你 循环 数组 code 和整数密钥 k ，请你返回解密后的结果来拆除炸弹！
## 解题思路
- 给出一个 code 数组，要求按照规则替换每个字母。
- 简单题，按照题意描述循环即可。
## 代码
```go
package leetcode
func decrypt(code []int, k int) []int {
if k == 0 {
for i := 0; i < len(code); i++ {
code[i] = 0
}
return code
}
count, sum, res := k, 0, make([]int, len(code))
if k > 0 {
for i := 0; i < len(code); i++ {
for j := i + 1; j < len(code); j++ {
if count == 0 {
break
}
sum += code[j]
count--
}
if count > 0 {
for j := 0; j < len(code); j++ {
if count == 0 {
break
}
sum += code[j]
count--
}
}
res[i] = sum
sum, count = 0, k
}
}
if k < 0 {
for i := 0; i < len(code); i++ {
for j := i - 1; j >= 0; j-- {
if count == 0 {
break
}
sum += code[j]
count++
}
if count < 0 {
for j := len(code) - 1; j >= 0; j-- {
if count == 0 {
break
}
sum += code[j]
count++
}
}
res[i] = sum
sum, count = 0, k
}
}
return res
}
```

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# [1653. Minimum Deletions to Make String Balanced](https://leetcode.com/problems/minimum-deletions-to-make-string-balanced/)
## 题目
You are given a string `s` consisting only of characters `'a'` and `'b'`.
You can delete any number of characters in `s` to make `s` **balanced**. `s` is **balanced** if there is no pair of indices `(i,j)` such that `i < j` and `s[i] = 'b'` and `s[j]= 'a'`.
Return *the **minimum** number of deletions needed to make* `s` ***balanced***.
**Example 1:**
```
Input: s = "aababbab"
Output: 2
Explanation: You can either:
Delete the characters at 0-indexed positions 2 and 6 ("aababbab" -> "aaabbb"), or
Delete the characters at 0-indexed positions 3 and 6 ("aababbab" -> "aabbbb").
```
**Example 2:**
```
Input: s = "bbaaaaabb"
Output: 2
Explanation: The only solution is to delete the first two characters.
```
**Constraints:**
- `1 <= s.length <= 105`
- `s[i]` is `'a'` or `'b'`.
## 题目大意
给你一个字符串 s ，它仅包含字符 'a' 和 'b' 。你可以删除 s 中任意数目的字符，使得 s 平衡 。我们称 s 平衡的 当不存在下标对 (i,j) 满足 i < j 且 s[i] = 'b' 同时 s[j]= 'a' 。请你返回使 s 平衡 的 最少 删除次数。
## 解题思路
- 给定一个字符串，要求删除最少次数，使得字母 a 都排在字母 b 的前面。
- 很容易想到的一个解题思路是 DP。定义 `dp[i]` 为字符串下标 [ 0, i ] 这个区间内使得字符串平衡的最少删除次数。当 `s[i] == 'a'` 的时候，有 2 种情况，一种是 `s[i]` 前面全是 `[aa……aa]` 的情况，这个时候只需要把其中的所有的字母 `b` 删除即可。还有一种情况是 `s[i]` 前面有字母 `a` 也有字母 `b`，即 `[aaa……abb……b]`，这种情况就需要考虑 `dp[i-1]` 了。当前字母是 `a`，那么肯定要删除字母 `a`，来维持前面有一段字母 `b` 的情况。当 `s[i] == 'b'` 的时候，不管是 `[aa……aa]` 这种情况，还是 `[aaa……abb……b]` 这种情况，当前字母 `b` 都可以直接附加在后面，也能保证整个字符串是平衡的。所以状态转移方程为 `dp[i+1] = min(dp[i] + 1, bCount), s[i] == 'a'`，`dp[i+1] = dp[i], s[i] == 'b'`。最终答案存在 `dp[n]` 中。由于前后项的递推关系中只用到一次前一项，所以我们还可以优化一下空间，用一个变量保存前一项的结果。优化以后的代码见解法一。
- 这一题还有一个模拟的思路。题目要求找到最小删除字数，那么就是要找到一个“临界点”，在这个临界点的左边删除所有的字母 b，在这个临界点的右边删除所有的字母 a。在所有的“临界点”中找到删除最少的次数。代码实现见解法二。
## 代码
```go
package leetcode
// 解法一 DP
func minimumDeletions(s string) int {
prev, res, bCount := 0, 0, 0
for _, c := range s {
if c == 'a' {
res = min(prev+1, bCount)
prev = res
} else {
bCount++
}
}
return res
}
func min(a, b int) int {
if a < b {
return a
}
return b
}
// 解法二 模拟
func minimumDeletions1(s string) int {
aCount, bCount, res := 0, 0, 0
for i := 0; i < len(s); i++ {
if s[i] == 'a' {
aCount++
}
}
res = aCount
for i := 0; i < len(s); i++ {
if s[i] == 'a' {
aCount--
} else {
bCount++
}
res = min(res, aCount+bCount)
}
return res
}
```

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# [1654. Minimum Jumps to Reach Home](https://leetcode.com/problems/minimum-jumps-to-reach-home/)
## 题目
A certain bug's home is on the x-axis at position `x`. Help them get there from position `0`.
The bug jumps according to the following rules:
- It can jump exactly `a` positions **forward** (to the right).
- It can jump exactly `b` positions **backward** (to the left).
- It cannot jump backward twice in a row.
- It cannot jump to any `forbidden` positions.
The bug may jump forward **beyond** its home, but it **cannot jump** to positions numbered with **negative** integers.
Given an array of integers `forbidden`, where `forbidden[i]` means that the bug cannot jump to the position `forbidden[i]`, and integers `a`, `b`, and `x`, return *the minimum number of jumps needed for the bug to reach its home*. If there is no possible sequence of jumps that lands the bug on position `x`, return `1.`
**Example 1:**
```
Input: forbidden = [14,4,18,1,15], a = 3, b = 15, x = 9
Output: 3
Explanation: 3 jumps forward (0 -> 3 -> 6 -> 9) will get the bug home.
```
**Example 2:**
```
Input: forbidden = [8,3,16,6,12,20], a = 15, b = 13, x = 11
Output: -1
```
**Example 3:**
```
Input: forbidden = [1,6,2,14,5,17,4], a = 16, b = 9, x = 7
Output: 2
Explanation: One jump forward (0 -> 16) then one jump backward (16 -> 7) will get the bug home.
```
**Constraints:**
- `1 <= forbidden.length <= 1000`
- `1 <= a, b, forbidden[i] <= 2000`
- `0 <= x <= 2000`
- All the elements in `forbidden` are distinct.
- Position `x` is not forbidden.
## 题目大意
有一只跳蚤的家在数轴上的位置 x 处。请你帮助它从位置 0 出发，到达它的家。
跳蚤跳跃的规则如下：
- 它可以 往前 跳恰好 a 个位置（即往右跳）。
- 它可以 往后 跳恰好 b 个位置（即往左跳）。
- 它不能 连续 往后跳 2 次。
- 它不能跳到任何 forbidden 数组中的位置。
跳蚤可以往前跳 超过 它的家的位置，但是它 不能跳到负整数 的位置。给你一个整数数组 forbidden ，其中 forbidden[i] 是跳蚤不能跳到的位置，同时给你整数 a， b 和 x ，请你返回跳蚤到家的最少跳跃次数。如果没有恰好到达 x 的可行方案，请你返回 -1 。
## 解题思路
- 给出坐标 x ，可以往前跳的步长 a，往后跳的步长 b。要求输出能跳回家的最少跳跃次数。
- 求最少跳跃次数，思路用 BFS 求解，最先到达坐标 x 的方案即是最少跳跃次数。对`forbidden` 的处理是把记忆化数组里面把他们标记为 true。禁止连续往后跳 2 次的限制，要求我们在 BFS 入队的时候再记录一下跳跃方向，每次往后跳的时候判断前一跳是否是往后跳，如果是往后跳，此次就不能往后跳了。
## 代码
```go
package leetcode
func minimumJumps(forbidden []int, a int, b int, x int) int {
visited := make([]bool, 6000)
for i := range forbidden {
visited[forbidden[i]] = true
}
queue, res := [][2]int{{0, 0}}, -1
for len(queue) > 0 {
length := len(queue)
res++
for i := 0; i < length; i++ {
cur, isBack := queue[i][0], queue[i][1]
if cur == x {
return res
}
if isBack == 0 && cur-b > 0 && !visited[cur-b] {
visited[cur-b] = true
queue = append(queue, [2]int{cur - b, 1})
}
if cur+a < len(visited) && !visited[cur+a] {
visited[cur+a] = true
queue = append(queue, [2]int{cur + a, 0})
}
}
queue = queue[length:]
}
return -1
}
```

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# [1655. Distribute Repeating Integers](https://leetcode.com/problems/distribute-repeating-integers/)
## 题目
You are given an array of `n` integers, `nums`, where there are at most `50` unique values in the array. You are also given an array of `m` customer order quantities, `quantity`, where `quantity[i]` is the amount of integers the `ith` customer ordered. Determine if it is possible to distribute `nums` such that:
- The `ith` customer gets **exactly** `quantity[i]` integers,
- The integers the `ith` customer gets are **all equal**, and
- Every customer is satisfied.
Return `true` *if it is possible to distribute* `nums` *according to the above conditions*.
**Example 1:**
```
Input: nums = [1,2,3,4], quantity = [2]
Output: false
Explanation: The 0th customer cannot be given two different integers.
```
**Example 2:**
```
Input: nums = [1,2,3,3], quantity = [2]
Output: true
Explanation: The 0th customer is given [3,3]. The integers [1,2] are not used.
```
**Example 3:**
```
Input: nums = [1,1,2,2], quantity = [2,2]
Output: true
Explanation: The 0th customer is given [1,1], and the 1st customer is given [2,2].
```
**Example 4:**
```
Input: nums = [1,1,2,3], quantity = [2,2]
Output: false
Explanation: Although the 0th customer could be given [1,1], the 1st customer cannot be satisfied.
```
**Example 5:**
```
Input: nums = [1,1,1,1,1], quantity = [2,3]
Output: true
Explanation: The 0th customer is given [1,1], and the 1st customer is given [1,1,1].
```
**Constraints:**
- `n == nums.length`
- `1 <= n <= 105`
- `1 <= nums[i] <= 1000`
- `m == quantity.length`
- `1 <= m <= 10`
- `1 <= quantity[i] <= 105`
- There are at most `50` unique values in `nums`.
## 题目大意
给你一个长度为 n 的整数数组 nums ，这个数组中至多有 50 个不同的值。同时你有 m 个顾客的订单 quantity ，其中，整数 quantity[i] 是第 i 位顾客订单的数目。请你判断是否能将 nums 中的整数分配给这些顾客，且满足：
- 第 i 位顾客 恰好 有 quantity[i] 个整数。
- 第 i 位顾客拿到的整数都是 相同的 。
- 每位顾客都满足上述两个要求。
如果你可以分配 nums 中的整数满足上面的要求，那么请返回 true ，否则返回 false 。
## 解题思路
- 给定一个数组 nums，订单数组 quantity，要求按照订单满足顾客的需求。如果能满足输出 true，不能满足输出 false。
- 用 DFS 记忆化暴力搜索。代码实现不难。（不知道此题为什么是 Hard）
## 代码
```go
package leetcode
func canDistribute(nums []int, quantity []int) bool {
freq := make(map[int]int)
for _, n := range nums {
freq[n]++
}
return dfs(freq, quantity)
}
func dfs(freq map[int]int, quantity []int) bool {
if len(quantity) == 0 {
return true
}
visited := make(map[int]bool)
for i := range freq {
if visited[freq[i]] {
continue
}
visited[freq[i]] = true
if freq[i] >= quantity[0] {
freq[i] -= quantity[0]
if dfs(freq, quantity[1:]) {
return true
}
freq[i] += quantity[0]
}
}
return false
}
```

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- [1647.Minimum-Deletions-to-Make-Character-Frequencies-Unique]({{< relref "/ChapterFour/1647.Minimum-Deletions-to-Make-Character-Frequencies-Unique.md" >}}) - [1647.Minimum-Deletions-to-Make-Character-Frequencies-Unique]({{< relref "/ChapterFour/1647.Minimum-Deletions-to-Make-Character-Frequencies-Unique.md" >}})
- [1648.Sell-Diminishing-Valued-Colored-Balls]({{< relref "/ChapterFour/1648.Sell-Diminishing-Valued-Colored-Balls.md" >}}) - [1648.Sell-Diminishing-Valued-Colored-Balls]({{< relref "/ChapterFour/1648.Sell-Diminishing-Valued-Colored-Balls.md" >}})
- [1649.Create-Sorted-Array-through-Instructions]({{< relref "/ChapterFour/1649.Create-Sorted-Array-through-Instructions.md" >}}) - [1649.Create-Sorted-Array-through-Instructions]({{< relref "/ChapterFour/1649.Create-Sorted-Array-through-Instructions.md" >}})
- [1652.Defuse-the-Bomb]({{< relref "/ChapterFour/1652.Defuse-the-Bomb.md" >}})
- [1653.Minimum-Deletions-to-Make-String-Balanced]({{< relref "/ChapterFour/1653.Minimum-Deletions-to-Make-String-Balanced.md" >}})
- [1654.Minimum-Jumps-to-Reach-Home]({{< relref "/ChapterFour/1654.Minimum-Jumps-to-Reach-Home.md" >}})
- [1655.Distribute-Repeating-Integers]({{< relref "/ChapterFour/1655.Distribute-Repeating-Integers.md" >}})
- [1656.Design-an-Ordered-Stream]({{< relref "/ChapterFour/1656.Design-an-Ordered-Stream.md" >}}) - [1656.Design-an-Ordered-Stream]({{< relref "/ChapterFour/1656.Design-an-Ordered-Stream.md" >}})
- [1657.Determine-if-Two-Strings-Are-Close]({{< relref "/ChapterFour/1657.Determine-if-Two-Strings-Are-Close.md" >}}) - [1657.Determine-if-Two-Strings-Are-Close]({{< relref "/ChapterFour/1657.Determine-if-Two-Strings-Are-Close.md" >}})
- [1658.Minimum-Operations-to-Reduce-X-to-Zero]({{< relref "/ChapterFour/1658.Minimum-Operations-to-Reduce-X-to-Zero.md" >}}) - [1658.Minimum-Operations-to-Reduce-X-to-Zero]({{< relref "/ChapterFour/1658.Minimum-Operations-to-Reduce-X-to-Zero.md" >}})