添加第15题. 三数之和JavaScript版本

problems/0015.三数之和.md

@@ -256,6 +256,59 @@ 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;
+};
+```