Add solution #668

Author: JoshCrozier

README.md

@@ -501,6 +501,7 @@
 662|[Maximum Width of Binary Tree](./0662-maximum-width-of-binary-tree.js)|Medium|
 664|[Strange Printer](./0664-strange-printer.js)|Hard|
 667|[Beautiful Arrangement II](./0667-beautiful-arrangement-ii.js)|Medium|
+668|[Kth Smallest Number in Multiplication Table](./0668-kth-smallest-number-in-multiplication-table.js)|Hard|
 680|[Valid Palindrome II](./0680-valid-palindrome-ii.js)|Easy|
 684|[Redundant Connection](./0684-redundant-connection.js)|Medium|
 686|[Repeated String Match](./0686-repeated-string-match.js)|Easy|

solutions/0668-kth-smallest-number-in-multiplication-table.js

@@ -0,0 +1,41 @@
+/**
+ * 668. Kth Smallest Number in Multiplication Table
+ * https://leetcode.com/problems/kth-smallest-number-in-multiplication-table/
+ * Difficulty: Hard
+ *
+ * Nearly everyone has used the Multiplication Table. The multiplication table of size m x n is
+ * an integer matrix mat where mat[i][j] == i * j (1-indexed).
+ *
+ * Given three integers m, n, and k, return the kth smallest element in the m x n multiplication
+ * table.
+ */
+
+/**
+ * @param {number} m
+ * @param {number} n
+ * @param {number} k
+ * @return {number}
+ */
+var findKthNumber = function(m, n, k) {
+  let low = 1;
+  let high = m * n;
+
+  while (low < high) {
+    const middle = Math.floor((low + high) / 2);
+    if (helper(middle) < k) {
+      low = middle + 1;
+    } else {
+      high = middle;
+    }
+  }
+
+  return low;
+
+  function helper(x) {
+    let count = 0;
+    for (let i = 1; i <= m; i++) {
+      count += Math.min(Math.floor(x / i), n);
+    }
+    return count;
+  }
+};