Add solution #1439

Author: JoshCrozier

README.md

@@ -1,4 +1,4 @@
-# 1,303 LeetCode solutions in JavaScript
+# 1,304 LeetCode solutions in JavaScript
 
 [https://leetcodejavascript.com](https://leetcodejavascript.com)
 
@@ -1098,6 +1098,7 @@
 1436|[Destination City](./solutions/1436-destination-city.js)|Easy|
 1437|[Check If All 1's Are at Least Length K Places Away](./solutions/1437-check-if-all-1s-are-at-least-length-k-places-away.js)|Easy|
 1438|[Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit](./solutions/1438-longest-continuous-subarray-with-absolute-diff-less-than-or-equal-to-limit.js)|Medium|
+1439|[Find the Kth Smallest Sum of a Matrix With Sorted Rows](./solutions/1439-find-the-kth-smallest-sum-of-a-matrix-with-sorted-rows.js)|Hard|
 1443|[Minimum Time to Collect All Apples in a Tree](./solutions/1443-minimum-time-to-collect-all-apples-in-a-tree.js)|Medium|
 1446|[Consecutive Characters](./solutions/1446-consecutive-characters.js)|Easy|
 1447|[Simplified Fractions](./solutions/1447-simplified-fractions.js)|Medium|

solutions/1439-find-the-kth-smallest-sum-of-a-matrix-with-sorted-rows.js

@@ -0,0 +1,34 @@
+/**
+ * 1439. Find the Kth Smallest Sum of a Matrix With Sorted Rows
+ * https://leetcode.com/problems/find-the-kth-smallest-sum-of-a-matrix-with-sorted-rows/
+ * Difficulty: Hard
+ *
+ * You are given an m x n matrix mat that has its rows sorted in non-decreasing order and
+ * an integer k.
+ *
+ * You are allowed to choose exactly one element from each row to form an array.
+ *
+ * Return the kth smallest array sum among all possible arrays.
+ */
+
+/**
+ * @param {number[][]} mat
+ * @param {number} k
+ * @return {number}
+ */
+var kthSmallest = function(mat, k) {
+  let sums = [0];
+  const rows = mat.length;
+
+  for (let row = 0; row < rows; row++) {
+    const nextSums = [];
+    for (const prevSum of sums) {
+      for (const num of mat[row]) {
+        nextSums.push(prevSum + num);
+      }
+    }
+    sums = nextSums.sort((a, b) => a - b).slice(0, Math.min(k, nextSums.length));
+  }
+
+  return sums[k - 1];
+};