leetcode 15

Author: geekplux

leetcode/15.js

@@ -0,0 +1,59 @@
+/**
+
+Given an array nums of n integers, are there elements a, b, c in nums such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.
+
+Note:
+
+The solution set must not contain duplicate triplets.
+
+Example:
+
+Given array nums = [-1, 0, 1, 2, -1, -4],
+
+A solution set is:
+[
+  [-1, 0, 1],
+  [-1, -1, 2]
+]
+
+*/
+
+/**
+ * @param {number[]} nums
+ * @return {number[][]}
+ */
+var threeSum = function(nums) {
+  const res = [];
+  if (nums.length < 3) {
+    return res;
+  }
+
+  nums = nums.sort((a, b) => a - b);
+
+  for (let i = 0; i < nums.length - 2; i++) {
+    if (nums[i] > 0) {
+      return res;
+    }
+    if (i > 0 && nums[i] == nums[i - 1]) {
+      continue;
+    }
+    for (let j = i + 1, k = nums.length - 1; j < k; ) {
+      if (nums[i] + nums[j] + nums[k] === 0) {
+        res.push([nums[i], nums[j], nums[k]]);
+        j++;
+        k--;
+        while (j < k && nums[j] == nums[j - 1]) {
+          j++;
+        }
+        while (j < k && nums[k] == nums[k + 1]) {
+          k--;
+        }
+      } else if (nums[i] + nums[j] + nums[k] > 0) {
+        k--;
+      } else {
+        j++;
+      }
+    }
+  }
+  return res;
+};