Add solution #611

Author: JoshCrozier

README.md

@@ -468,6 +468,7 @@
 605|[Can Place Flowers](./0605-can-place-flowers.js)|Easy|
 606|[Construct String from Binary Tree](./0606-construct-string-from-binary-tree.js)|Easy|
 609|[Find Duplicate File in System](./0609-find-duplicate-file-in-system.js)|Medium|
+611|[Valid Triangle Number](./0611-valid-triangle-number.js)|Medium|
 617|[Merge Two Binary Trees](./0617-merge-two-binary-trees.js)|Easy|
 621|[Task Scheduler](./0621-task-scheduler.js)|Medium|
 628|[Maximum Product of Three Numbers](./0628-maximum-product-of-three-numbers.js)|Easy|

solutions/0611-valid-triangle-number.js

@@ -0,0 +1,31 @@
+/**
+ * 611. Valid Triangle Number
+ * https://leetcode.com/problems/valid-triangle-number/
+ * Difficulty: Medium
+ *
+ * Given an integer array nums, return the number of triplets chosen from the array that
+ * can make triangles if we take them as side lengths of a triangle.
+ */
+
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var triangleNumber = function(nums) {
+  let count = 0;
+
+  nums.sort((a, b) => a - b);
+
+  for (let k = nums.length - 1; k >= 2; k--) {
+    for (let i = 0, j = k - 1; i < j;) {
+      if (nums[i] + nums[j] > nums[k]) {
+        count += j - i;
+        j--;
+      } else {
+        i++;
+      }
+    }
+  }
+
+  return count;
+};