Merge branch 'youngyangyang04:master' into master

This commit is contained in:
hailincai
2021-10-17 09:29:57 -04:00
committed by GitHub
4 changed files with 101 additions and 88 deletions

View File

@ -293,85 +293,40 @@ class Solution:
"""
Do not return anything, modify board in-place instead.
"""
def backtrack(board):
for i in range(len(board)): #遍历行
for j in range(len(board[0])): #遍历列
if board[i][j] != ".": continue
for k in range(1,10): #(i, j) 这个位置放k是否合适
if isValid(i,j,k,board):
board[i][j] = str(k) #放置k
if backtrack(board): return True #如果找到合适一组立刻返回
board[i][j] = "." #回溯撤销k
return False #9个数都试完了都不行那么就返回false
return True #遍历完没有返回false说明找到了合适棋盘位置了
def isValid(row,col,val,board):
for i in range(9): #判断行里是否重复
if board[row][i] == str(val):
self.backtracking(board)
def backtracking(self, board: List[List[str]]) -> bool:
# 若有解返回True若无解返回False
for i in range(len(board)): # 遍历行
for j in range(len(board[0])): # 遍历列
# 若空格内已有数字,跳过
if board[i][j] != '.': continue
for k in range(1, 10):
if self.is_valid(i, j, k, board):
board[i][j] = str(k)
if self.backtracking(board): return True
board[i][j] = '.'
# 若数字1-9都不能成功填入空格返回False无解
return False
return True # 有解
def is_valid(self, row: int, col: int, val: int, board: List[List[str]]) -> bool:
# 判断同一行是否冲突
for i in range(9):
if board[row][i] == str(val):
return False
# 判断同一列是否冲突
for j in range(9):
if board[j][col] == str(val):
return False
# 判断同一九宫格是否有冲突
start_row = (row // 3) * 3
start_col = (col // 3) * 3
for i in range(start_row, start_row + 3):
for j in range(start_col, start_col + 3):
if board[i][j] == str(val):
return False
for j in range(9): #判断列里是否重复
if board[j][col] == str(val):
return False
startRow = (row // 3) * 3
startcol = (col // 3) * 3
for i in range(startRow,startRow + 3): #判断9方格里是否重复
for j in range(startcol,startcol + 3):
if board[i][j] == str(val):
return False
return True
backtrack(board)
```
Python3:
```python3
class Solution:
def __init__(self) -> None:
self.board = []
def isValid(self, row: int, col: int, target: int) -> bool:
for idx in range(len(self.board)):
# 同列是否重复
if self.board[idx][col] == str(target):
return False
# 同行是否重复
if self.board[row][idx] == str(target):
return False
# 9宫格里是否重复
box_row, box_col = (row // 3) * 3 + idx // 3, (col // 3) * 3 + idx % 3
if self.board[box_row][box_col] == str(target):
return False
return True
def getPlace(self) -> List[int]:
for row in range(len(self.board)):
for col in range(len(self.board)):
if self.board[row][col] == ".":
return [row, col]
return [-1, -1]
def isSolved(self) -> bool:
row, col = self.getPlace() # 找个空位置
if row == -1 and col == -1: # 没有空位置,棋盘被填满的
return True
for i in range(1, 10):
if self.isValid(row, col, i): # 检查这个空位置放i是否合适
self.board[row][col] = str(i) # 放i
if self.isSolved(): # 合适,立刻返回, 填下一个空位置。
return True
self.board[row][col] = "." # 不合适,回溯
return False # 空位置没法解决
def solveSudoku(self, board: List[List[str]]) -> None:
"""
Do not return anything, modify board in-place instead.
"""
if board is None or len(board) == 0:
return
self.board = board
self.isSolved()
```
Go

View File

@ -368,6 +368,41 @@ class Solution:
return (val1, val2)
```
Go:
> 动态规划
```go
func rob(root *TreeNode) int {
res := robTree(root)
return max(res[0], res[1])
}
func max(a, b int) int {
if a > b {
return a
}
return b
}
func robTree(cur *TreeNode) []int {
if cur == nil {
return []int{0, 0}
}
// 后序遍历
left := robTree(cur.Left)
right := robTree(cur.Right)
// 考虑去偷当前的屋子
robCur := cur.Val + left[0] + right[0]
// 考虑不去偷当前的屋子
notRobCur := max(left[0], left[1]) + max(right[0], right[1])
// 注意顺序0:不偷1:去偷
return []int{notRobCur, robCur}
}
```
JavaScript
> 动态规划

View File

@ -226,6 +226,32 @@ class Solution:
return taraget == dp[taraget]
```
Go
```go
// 分割等和子集 动态规划
// 时间复杂度O(n^2) 空间复杂度O(n)
func canPartition(nums []int) bool {
sum := 0
for _, num := range nums {
sum += num
}
// 如果 nums 的总和为奇数则不可能平分成两个子集
if sum % 2 == 1 {
return false
}
target := sum / 2
dp := make([]int, target + 1)
for _, num := range nums {
for j := target; j >= num; j-- {
if dp[j] < dp[j - num] + num {
dp[j] = dp[j - num] + num
}
}
}
return dp[target] == target
}
```
```go
func canPartition(nums []int) bool {

View File

@ -200,17 +200,14 @@ func reverse(b []byte, left, right int){
JavaScript
```javascript
var reverseLeftWords = function (s, n) {
const reverse = (str, left, right) => {
let strArr = str.split("");
for (; left < right; left++, right--) {
[strArr[left], strArr[right]] = [strArr[right], strArr[left]];
}
return strArr.join("");
}
s = reverse(s, 0, n - 1);
s = reverse(s, n, s.length - 1);
return reverse(s, 0, s.length - 1);
var reverseLeftWords = function(s, n) {
const length = s.length;
let i = 0;
while (i < length - n) {
s = s[length - 1] + s;
i++;
}
return s.slice(0, length);
};
```