Merge pull request #228 from flames519/master

0242，0349，0454， 0383，015 JavaScript版本

problems/0015.三数之和.md

@@ -281,6 +281,59 @@ func threeSum(nums []int)[][]int{
 }
 ```
 
+javaScript: 
+
+```js
+/**
+ * @param {number[]} nums
+ * @return {number[][]}
+ */
+
+// 循环内不考虑去重 
+var threeSum = function(nums) {
+    const len = nums.length;
+    if(len < 3) return [];
+    nums.sort((a, b) => a - b);
+    const resSet = new Set();
+    for(let i = 0; i < len - 2; i++) {
+        if(nums[i] > 0) break;
+        let l = i + 1, r = len - 1;
+        while(l < r) {
+            const sum = nums[i] + nums[l] + nums[r];
+            if(sum < 0) { l++; continue };
+            if(sum > 0) { r--; continue };
+            resSet.add(`${nums[i]},${nums[l]},${nums[r]}`);
+            l++;
+            r--;
+        }
+    }
+    return Array.from(resSet).map(i => i.split(","));
+};
+
+// 去重优化
+var threeSum = function(nums) {
+    const len = nums.length;
+    if(len < 3) return [];
+    nums.sort((a, b) => a - b);
+    const res = [];
+    for(let i = 0; i < len - 2; i++) {
+        if(nums[i] > 0) break;
+        // a去重
+        if(i > 0 && nums[i] === nums[i - 1]) continue;
+        let l = i + 1, r = len - 1;
+        while(l < r) {
+            const sum = nums[i] + nums[l] + nums[r];
+            if(sum < 0) { l++; continue };
+            if(sum > 0) { r--; continue };
+            res.push([nums[i], nums[l], nums[r]])
+            // b c 去重 
+            while(l < r && nums[l] === nums[++l]);
+            while(l < r && nums[r] === nums[--r]);
+        }
+    }
+    return res;
+};
+```
 
 
 

problems/0018.四数之和.md

@@ -201,7 +201,39 @@ class Solution(object):
 
 Go：
 
+javaScript: 
 
+```js
+/**
+ * @param {number[]} nums
+ * @param {number} target
+ * @return {number[][]}
+ */
+var fourSum = function(nums, target) {
+    const len = nums.length;
+    if(len < 4) return [];
+    nums.sort((a, b) => a - b);
+    const res = [];
+    for(let i = 0; i < len - 3; i++) {
+        // 去重i
+        if(i > 0 && nums[i] === nums[i - 1]) continue;
+        for(let j = i + 1; j < len - 2; j++) {
+            // 去重j
+            if(j > i + 1 && nums[j] === nums[j - 1]) continue;
+            let l = j + 1, r = len - 1;
+            while(l < r) {
+                const sum = nums[i] + nums[j] + nums[l] + nums[r];
+                if(sum < target) { l++; continue}
+                if(sum > target) { r--; continue}
+                res.push([nums[i], nums[j], nums[l], nums[r]]);
+                while(l < r && nums[l] === nums[++l]);
+                while(l < r && nums[r] === nums[--r]);
+            }
+        } 
+    }
+    return res;
+};
+```
 
 
 -----------------------

problems/0242.有效的字母异位词.md

@@ -140,6 +140,29 @@ func isAnagram(s string, t string) bool {
 }
 ```
 
+javaScript:
+
+```js
+/**
+ * @param {string} s
+ * @param {string} t
+ * @return {boolean}
+ */
+var isAnagram = function(s, t) {
+    if(s.length !== t.length) return false;
+    const resSet = new Array(26).fill(0);
+    const base = "a".charCodeAt();
+    for(const i of s) {
+        resSet[i.charCodeAt() - base]++;
+    }
+    for(const i of t) {
+        if(!resSet[i.charCodeAt() - base]) return false;
+        resSet[i.charCodeAt() - base]--;
+    }
+    return true;
+};
+```
+
 ## 相关题目
 
 * 383.赎金信

problems/0349.两个数组的交集.md

@@ -113,6 +113,34 @@ Python：
 
 Go：
 
+javaScript:
+
+```js
+/**
+ * @param {number[]} nums1
+ * @param {number[]} nums2
+ * @return {number[]}
+ */
+var intersection = function(nums1, nums2) {
+    // 根据数组大小交换操作的数组
+    if(nums1.length < nums2.length) {
+        const _ = nums1;
+        nums1 = nums2;
+        nums2 = _;
+    }
+    const nums1Set = new Set(nums1);
+    const resSet = new Set();
+    // for(const n of nums2) {
+    //     nums1Set.has(n) && resSet.add(n);
+    // }
+    // 循环 比 迭代器快
+    for(let i = nums2.length - 1; i >= 0; i--) {
+        nums1Set.has(nums2[i]) && resSet.add(nums2[i]);
+    }
+    return Array.from(resSet);
+};
+```
+
 
 
 

problems/0383.赎金信.md

@@ -136,7 +136,7 @@ class Solution {
 ```
 
 Python：
-```
+```py
 class Solution(object):
     def canConstruct(self, ransomNote, magazine):
         """
@@ -167,6 +167,28 @@ class Solution(object):
 
 Go：
 
+javaScript:
+
+```js
+/**
+ * @param {string} ransomNote
+ * @param {string} magazine
+ * @return {boolean}
+ */
+var canConstruct = function(ransomNote, magazine) {
+    const strArr = new Array(26).fill(0), 
+        base = "a".charCodeAt();
+    for(const s of magazine) {
+        strArr[s.charCodeAt() - base]++;
+    }
+    for(const s of ransomNote) {
+        const index = s.charCodeAt() - base;
+        if(!strArr[index]) return false;
+        strArr[index]--;
+    }
+    return true;
+};
+```
 
 
 

problems/0454.四数相加II.md

@@ -155,6 +155,38 @@ class Solution(object):
 
 Go：
 
+javaScript: 
+
+```js
+/**
+ * @param {number[]} nums1
+ * @param {number[]} nums2
+ * @param {number[]} nums3
+ * @param {number[]} nums4
+ * @return {number}
+ */
+var fourSumCount = function(nums1, nums2, nums3, nums4) {
+    const twoSumMap = new Map();
+    let count = 0;
+
+    for(const n1 of nums1) {
+        for(const n2 of nums2) {
+            const sum = n1 + n2;
+            twoSumMap.set(sum, (twoSumMap.get(sum) || 0) + 1)
+        }
+    }
+
+    for(const n3 of nums3) {
+        for(const n4 of nums4) {
+            const sum = n3 + n4;
+            count += (twoSumMap.get(0 - sum) || 0)
+        }
+    }
+
+    return count;
+};
+```
+