day-1三数之和

70works/day1_threeSum.js

+/*
+ * @Author: your name
+ * @Date: 2020-08-24 23:17:23
+ * @LastEditTime: 2020-08-25 01:14:49
+ * @LastEditors: Please set LastEditors
+ * @Description: In User Settings Edit
+ * @FilePath: \70works\day1_threeSum.js
+ */
+/**
+ * @param {number[]} nums
+ * @return {number[][]}
+ */
+var threeSum = function(nums) {
+    let res = [];
+    let len = nums.length;
+    nums.sort((a,b)=>a-b);
+
+    // leetcode上不能直接return,而要具体返回一个对象才行;
+    //否则会报错；输入为空,输出为undefined;
+    if(len <0 || len < 3)return res;
+    for(let i =0; i< len; i++) {
+        let L = i+1;
+        let R = len-1;
+        if(nums[i]>0) break;
+        if(i>0 && nums[i] == nums[i-1])continue;
+        while(L < R) {
+            const sum = nums[i]+nums[L]+nums[R];
+            if(sum === 0) {
+                res.push([nums[i],nums[L],nums[R]]);
+                while(L<R && nums[L]==nums[L+1]) L++;
+                while(L<R && nums[R] == nums[R+1])R--;
+                L++;
+                R--;
+
+            }else if (sum<0){
+                L++;
+            }else if(sum>0){
+                R--;
+            }
+        }
+    }
+    return res;
+};
+let nums = [-1, 0, 1, 2, -1, -4]
+threeSum(nums);
+// module.exports = threeSum;