From e86fea0ec398e8161149377a0fc5c5480ae680d0 Mon Sep 17 00:00:00 2001 From: Yuhao Ju Date: Thu, 24 Nov 2022 21:07:05 +0800 Subject: [PATCH 1/7] =?UTF-8?q?update=200242.=E6=9C=89=E6=95=88=E7=9A=84?= =?UTF-8?q?=E5=AD=97=E6=AF=8D=E5=BC=82=E4=BD=8D=E8=AF=8D=EF=BC=9A=E5=8A=A0?= =?UTF-8?q?java=E6=B3=A8=E9=87=8A=EF=BC=8C=E5=88=A0=E9=99=A4=E8=B4=A8?= =?UTF-8?q?=E9=87=8F=E8=BE=83=E5=B7=AE=E4=B8=94=E5=A4=9A=E4=BD=99=E7=9A=84?= =?UTF-8?q?go=E4=BB=A3=E7=A0=81?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0242.有效的字母异位词.md | 35 ++++------------------- 1 file changed, 5 insertions(+), 30 deletions(-) diff --git a/problems/0242.有效的字母异位词.md b/problems/0242.有效的字母异位词.md index 1281b16b..904a0527 100644 --- a/problems/0242.有效的字母异位词.md +++ b/problems/0242.有效的字母异位词.md @@ -101,7 +101,7 @@ class Solution { int[] record = new int[26]; for (int i = 0; i < s.length(); i++) { - record[s.charAt(i) - 'a']++; + record[s.charAt(i) - 'a']++; // 并不需要记住字符a的ASCII，只要求出一个相对数值就可以了 } for (int i = 0; i < t.length(); i++) { @@ -109,11 +109,11 @@ class Solution { } for (int count: record) { - if (count != 0) { + if (count != 0) { // record数组如果有的元素不为零0，说明字符串s和t 一定是谁多了字符或者谁少了字符。 return false; } } - return true; + return true; // record数组所有元素都为零0，说明字符串s和t是字母异位词 } } ``` @@ -166,35 +166,10 @@ class Solution(object): Go： -```go -func isAnagram(s string, t string) bool { - if len(s)!=len(t){ - return false - } - exists := make(map[byte]int) - for i:=0;i=0&&ok{ - exists[s[i]]=v+1 - }else{ - exists[s[i]]=1 - } - } - for i:=0;i=1&&ok{ - exists[t[i]]=v-1 - }else{ - return false - } - } - return true -} -``` - -Go写法二（没有使用slice作为哈希表，用数组来代替）： - ```go func isAnagram(s string, t string) bool { record := [26]int{} + for _, r := range s { record[r-rune('a')]++ } @@ -202,7 +177,7 @@ func isAnagram(s string, t string) bool { record[r-rune('a')]-- } - return record == [26]int{} + return record == [26]int{} // record数组如果有的元素不为零0，说明字符串s和t 一定是谁多了字符或者谁少了字符。 } ``` From ac58e6613bd6a9d3e265e95e285c40b05bbc6f29 Mon Sep 17 00:00:00 2001 From: Yuhao Ju Date: Thu, 24 Nov 2022 21:26:09 +0800 Subject: [PATCH 2/7] =?UTF-8?q?update=200349.=E4=B8=A4=E4=B8=AA=E6=95=B0?= =?UTF-8?q?=E7=BB=84=E7=9A=84=E4=BA=A4=E9=9B=86=20=E4=BF=AE=E6=94=B9python?= =?UTF-8?q?=E4=BB=A3=E7=A0=81=EF=BC=8C=E5=88=A0=E9=99=A4=E5=86=97=E4=BD=99?= =?UTF-8?q?=E7=9A=84go=E4=BB=A3=E7=A0=81?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0349.两个数组的交集.md | 32 ++++++++++---------------- 1 file changed, 12 insertions(+), 20 deletions(-) diff --git a/problems/0349.两个数组的交集.md b/problems/0349.两个数组的交集.md index bd83fae9..2e98ef6f 100644 --- a/problems/0349.两个数组的交集.md +++ b/problems/0349.两个数组的交集.md @@ -147,32 +147,24 @@ Python3： ```python class Solution: def intersection(self, nums1: List[int], nums2: List[int]) -> List[int]: - return list(set(nums1) & set(nums2)) # 两个数组先变成集合，求交集后还原为数组 + val_dict = {} + ans = [] + for num in nums1: + val_dict[num] = 1 + + for num in nums2: + if num in val_dict.keys() and val_dict[num] == 1: + ans.append(num) + val_dict[num] = 0 + + return ans ``` Go： ```go func intersection(nums1 []int, nums2 []int) []int { - m := make(map[int]int) - for _, v := range nums1 { - m[v] = 1 - } - var res []int - // 利用count>0，实现重复值只拿一次放入返回结果中 - for _, v := range nums2 { - if count, ok := m[v]; ok && count > 0 { - res = append(res, v) - m[v]-- - } - } - return res -} -``` -```golang -//优化版，利用set，减少count统计 -func intersection(nums1 []int, nums2 []int) []int { - set:=make(map[int]struct{},0) + set:=make(map[int]struct{},0) // 用map模拟set res:=make([]int,0) for _,v:=range nums1{ if _,ok:=set[v];!ok{ From 4796c816421924edff6bdc2521ae0880e2d80f39 Mon Sep 17 00:00:00 2001 From: Yuhao Ju Date: Thu, 24 Nov 2022 21:35:53 +0800 Subject: [PATCH 3/7] =?UTF-8?q?update=200001.=E4=B8=A4=E6=95=B0=E4=B9=8B?= =?UTF-8?q?=E5=92=8C=EF=BC=9A=E5=8A=A0=E6=B3=A8=E9=87=8A=EF=BC=8C=E7=BB=99?= =?UTF-8?q?java=E4=BB=A3=E7=A0=81=E4=B8=80=E7=82=B9=E4=BC=98=E5=8C=96?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0001.两数之和.md | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/problems/0001.两数之和.md b/problems/0001.两数之和.md index 7bada9af..56cff527 100644 --- a/problems/0001.两数之和.md +++ b/problems/0001.两数之和.md @@ -134,12 +134,13 @@ public int[] twoSum(int[] nums, int target) { } Map map = new HashMap<>(); for(int i = 0; i < nums.length; i++){ - int temp = target - nums[i]; + int temp = target - nums[i]; // 遍历当前元素，并在map中寻找是否有匹配的key if(map.containsKey(temp)){ res[1] = i; res[0] = map.get(temp); + break; } - map.put(nums[i], i); + map.put(nums[i], i); // 如果没找到匹配对，就把访问过的元素和下标加入到map中 } return res; } @@ -152,16 +153,17 @@ class Solution: def twoSum(self, nums: List[int], target: int) -> List[int]: records = dict() - for index, value in enumerate(nums): - if target - value in records: + for index, value in enumerate(nums): + if target - value in records: # 遍历当前元素，并在map中寻找是否有匹配的key return [records[target- value], index] - records[value] = index + records[value] = index # 遍历当前元素，并在map中寻找是否有匹配的key return [] ``` Go： ```go +// 暴力解法 func twoSum(nums []int, target int) []int { for k1, _ := range nums { for k2 := k1 + 1; k2 < len(nums); k2++ { @@ -216,11 +218,11 @@ Javascript ```javascript var twoSum = function (nums, target) { let hash = {}; - for (let i = 0; i < nums.length; i++) { + for (let i = 0; i < nums.length; i++) { // 遍历当前元素，并在map中寻找是否有匹配的key if (hash[target - nums[i]] !== undefined) { return [i, hash[target - nums[i]]]; } - hash[nums[i]] = i; + hash[nums[i]] = i; // 如果没找到匹配对，就把访问过的元素和下标加入到map中 } return []; }; From b0f84a4b357f1413118536e55f6c37c460d32674 Mon Sep 17 00:00:00 2001 From: Yuhao Ju Date: Thu, 24 Nov 2022 21:42:38 +0800 Subject: [PATCH 4/7] =?UTF-8?q?update=200454.=E5=9B=9B=E6=95=B0=E7=9B=B8?= =?UTF-8?q?=E5=8A=A0II=EF=BC=9A=E5=AE=8C=E5=96=84=E6=B3=A8=E9=87=8A?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0454.四数相加II.md | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/problems/0454.四数相加II.md b/problems/0454.四数相加II.md index d9fd5c04..07c3f711 100644 --- a/problems/0454.四数相加II.md +++ b/problems/0454.四数相加II.md @@ -168,13 +168,15 @@ Go： ```go func fourSumCount(nums1 []int, nums2 []int, nums3 []int, nums4 []int) int { - m := make(map[int]int) + m := make(map[int]int) //key:a+b的数值，value:a+b数值出现的次数 count := 0 - for _, v1 := range nums1 { + // 遍历nums1和nums2数组，统计两个数组元素之和，和出现的次数，放到map中 + for _, v1 := range nums1 { for _, v2 := range nums2 { m[v1+v2]++ } } + // 遍历nums3和nums4数组，找到如果 0-(c+d) 在map中出现过的话，就把map中key对应的value也就是出现次数统计出来 for _, v3 := range nums3 { for _, v4 := range nums4 { count += m[-v3-v4] @@ -197,14 +199,14 @@ javaScript: var fourSumCount = function(nums1, nums2, nums3, nums4) { const twoSumMap = new Map(); let count = 0; - + // 统计nums1和nums2数组元素之和，和出现的次数，放到map中 for(const n1 of nums1) { for(const n2 of nums2) { const sum = n1 + n2; twoSumMap.set(sum, (twoSumMap.get(sum) || 0) + 1) } } - + // 找到如果 0-(c+d) 在map中出现过的话，就把map中key对应的value也就是出现次数统计出来 for(const n3 of nums3) { for(const n4 of nums4) { const sum = n3 + n4; From 983bb606d39c8ea5ab384d15d8c1bb226b65bce9 Mon Sep 17 00:00:00 2001 From: Yuhao Ju Date: Thu, 24 Nov 2022 21:51:48 +0800 Subject: [PATCH 5/7] =?UTF-8?q?update=200383.=E8=B5=8E=E9=87=91=E4=BF=A1:?= =?UTF-8?q?=20=E5=AE=8C=E5=96=84=E6=B3=A8=E9=87=8A?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0383.赎金信.md | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/problems/0383.赎金信.md b/problems/0383.赎金信.md index 57458308..4e6ba033 100644 --- a/problems/0383.赎金信.md +++ b/problems/0383.赎金信.md @@ -147,11 +147,11 @@ class Solution: arr = [0] * 26 - for x in magazine: + for x in magazine: # 记录 magazine里各个字符出现次数 arr[ord(x) - ord('a')] += 1 - for x in ransomNote: - if arr[ord(x) - ord('a')] == 0: + for x in ransomNote: # 在arr里对应的字符个数做--操作 + if arr[ord(x) - ord('a')] == 0: # 如果没有出现过直接返回 return False else: arr[ord(x) - ord('a')] -= 1 @@ -234,12 +234,12 @@ Go： ```go func canConstruct(ransomNote string, magazine string) bool { record := make([]int, 26) - for _, v := range magazine { + for _, v := range magazine { // 通过recode数据记录 magazine里各个字符出现次数 record[v-'a']++ } - for _, v := range ransomNote { + for _, v := range ransomNote { // 遍历ransomNote，在record里对应的字符个数做--操作 record[v-'a']-- - if record[v-'a'] < 0 { + if record[v-'a'] < 0 { // 如果小于零说明ransomNote里出现的字符，magazine没有 return false } } @@ -258,12 +258,12 @@ javaScript: var canConstruct = function(ransomNote, magazine) { const strArr = new Array(26).fill(0), base = "a".charCodeAt(); - for(const s of magazine) { + for(const s of magazine) { // 记录 magazine里各个字符出现次数 strArr[s.charCodeAt() - base]++; } - for(const s of ransomNote) { + for(const s of ransomNote) { // 对应的字符个数做--操作 const index = s.charCodeAt() - base; - if(!strArr[index]) return false; + if(!strArr[index]) return false; // 如果没记录过直接返回false strArr[index]--; } return true; From dddbb95ea718c7dfd327b270b4686a745d1e848d Mon Sep 17 00:00:00 2001 From: Yuhao Ju Date: Thu, 24 Nov 2022 22:05:59 +0800 Subject: [PATCH 6/7] =?UTF-8?q?update=200015.=E4=B8=89=E6=95=B0=E4=B9=8B?= =?UTF-8?q?=E5=92=8C=EF=BC=9A=E5=AE=8C=E5=96=84=E6=B3=A8=E9=87=8A=EF=BC=8C?= =?UTF-8?q?=E4=BC=98=E5=8C=96go=E4=BB=A3=E7=A0=81=E9=A3=8E=E6=A0=BC?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0015.三数之和.md | 56 +++++++++++++++++++++-------------- 1 file changed, 33 insertions(+), 23 deletions(-) diff --git a/problems/0015.三数之和.md b/problems/0015.三数之和.md index 5ee57127..6675e408 100644 --- a/problems/0015.三数之和.md +++ b/problems/0015.三数之和.md @@ -253,13 +253,15 @@ class Solution { public List> threeSum(int[] nums) { List> result = new ArrayList<>(); Arrays.sort(nums); - + // 找出a + b + c = 0 + // a = nums[i], b = nums[left], c = nums[right] for (int i = 0; i < nums.length; i++) { - if (nums[i] > 0) { + // 排序之后如果第一个元素已经大于零，那么无论如何组合都不可能凑成三元组，直接返回结果就可以了 + if (nums[i] > 0) { return result; } - if (i > 0 && nums[i] == nums[i - 1]) { + if (i > 0 && nums[i] == nums[i - 1]) { // 去重a continue; } @@ -273,7 +275,7 @@ class Solution { left++; } else { result.add(Arrays.asList(nums[i], nums[left], nums[right])); - + // 去重逻辑应该放在找到一个三元组之后，对b 和 c去重 while (right > left && nums[right] == nums[right - 1]) right--; while (right > left && nums[left] == nums[left + 1]) left++; @@ -294,12 +296,15 @@ class Solution: ans = [] n = len(nums) nums.sort() + # 找出a + b + c = 0 + # a = nums[i], b = nums[left], c = nums[right] for i in range(n): left = i + 1 right = n - 1 - if nums[i] > 0: + # 排序之后如果第一个元素已经大于零，那么无论如何组合都不可能凑成三元组，直接返回结果就可以了 + if nums[i] > 0: break - if i >= 1 and nums[i] == nums[i - 1]: + if i >= 1 and nums[i] == nums[i - 1]: # 去重a continue while left < right: total = nums[i] + nums[left] + nums[right] @@ -309,13 +314,14 @@ class Solution: left += 1 else: ans.append([nums[i], nums[left], nums[right]]) + # 去重逻辑应该放在找到一个三元组之后，对b 和 c去重 while left != right and nums[left] == nums[left + 1]: left += 1 while left != right and nums[right] == nums[right - 1]: right -= 1 left += 1 right -= 1 return ans ``` -Python (v2): +Python (v3): ```python class Solution: @@ -344,32 +350,36 @@ class Solution: Go： ```Go -func threeSum(nums []int)[][]int{ +func threeSum(nums []int) [][]int { sort.Ints(nums) - res:=[][]int{} - - for i:=0;i0{ + res := [][]int{} + // 找出a + b + c = 0 + // a = nums[i], b = nums[left], c = nums[right] + for i := 0; i < len(nums)-2; i++ { + // 排序之后如果第一个元素已经大于零，那么无论如何组合都不可能凑成三元组，直接返回结果就可以了 + n1 := nums[i] + if n1 > 0 { break } - if i>0&&n1==nums[i-1]{ + // 去重a + if i > 0 && n1 == nums[i-1] { continue } - l,r:=i+1,len(nums)-1 - for l Date: Thu, 24 Nov 2022 22:12:59 +0800 Subject: [PATCH 7/7] =?UTF-8?q?update=200018.=E5=9B=9B=E6=95=B0=E4=B9=8B?= =?UTF-8?q?=E5=92=8C=20=E5=AE=8C=E5=96=84=E6=B3=A8=E9=87=8A?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- problems/0018.四数之和.md | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) diff --git a/problems/0018.四数之和.md b/problems/0018.四数之和.md index ca33eb57..3fc80bba 100644 --- a/problems/0018.四数之和.md +++ b/problems/0018.四数之和.md @@ -136,25 +136,26 @@ class Solution { Arrays.sort(nums); for (int i = 0; i < nums.length; i++) { - + // nums[i] > target 直接返回, 剪枝操作 if (nums[i] > 0 && nums[i] > target) { return result; } - - if (i > 0 && nums[i - 1] == nums[i]) { + + if (i > 0 && nums[i - 1] == nums[i]) { // 对nums[i]去重 continue; } for (int j = i + 1; j < nums.length; j++) { - if (j > i + 1 && nums[j - 1] == nums[j]) { + if (j > i + 1 && nums[j - 1] == nums[j]) { // 对nums[j]去重 continue; } int left = j + 1; int right = nums.length - 1; while (right > left) { + // nums[k] + nums[i] + nums[left] + nums[right] > target int会溢出 long sum = (long) nums[i] + nums[j] + nums[left] + nums[right]; if (sum > target) { right--; @@ -162,7 +163,7 @@ class Solution { left++; } else { result.add(Arrays.asList(nums[i], nums[j], nums[left], nums[right])); - + // 对nums[left]和nums[right]去重 while (right > left && nums[right] == nums[right - 1]) right--; while (right > left && nums[left] == nums[left + 1]) left++; @@ -186,10 +187,10 @@ class Solution: nums.sort() n = len(nums) res = [] - for i in range(n): - if i > 0 and nums[i] == nums[i - 1]: continue + for i in range(n): + if i > 0 and nums[i] == nums[i - 1]: continue # 对nums[i]去重 for k in range(i+1, n): - if k > i + 1 and nums[k] == nums[k-1]: continue + if k > i + 1 and nums[k] == nums[k-1]: continue # 对nums[k]去重 p = k + 1 q = n - 1 @@ -198,6 +199,7 @@ class Solution: elif nums[i] + nums[k] + nums[p] + nums[q] < target: p += 1 else: res.append([nums[i], nums[k], nums[p], nums[q]]) + # 对nums[p]和nums[q]去重 while p < q and nums[p] == nums[p + 1]: p += 1 while p < q and nums[q] == nums[q - 1]: q -= 1 p += 1 @@ -258,12 +260,12 @@ func fourSum(nums []int, target int) [][]int { // if n1 > target { // 不能这样写,因为可能是负数 // break // } - if i > 0 && n1 == nums[i-1] { + if i > 0 && n1 == nums[i-1] { // 对nums[i]去重 continue } for j := i + 1; j < len(nums)-2; j++ { n2 := nums[j] - if j > i+1 && n2 == nums[j-1] { + if j > i+1 && n2 == nums[j-1] { // 对nums[j]去重 continue } l := j + 1 @@ -320,6 +322,8 @@ var fourSum = function(nums, target) { if(sum < target) { l++; continue} if(sum > target) { r--; continue} res.push([nums[i], nums[j], nums[l], nums[r]]); + + // 对nums[left]和nums[right]去重 while(l < r && nums[l] === nums[++l]); while(l < r && nums[r] === nums[--r]); }