Add solution #931

Author: JoshCrozier

README.md

@@ -740,6 +740,7 @@
 928|[Minimize Malware Spread II](./solutions/0928-minimize-malware-spread-ii.js)|Hard|
 929|[Unique Email Addresses](./solutions/0929-unique-email-addresses.js)|Easy|
 930|[Binary Subarrays With Sum](./solutions/0930-binary-subarrays-with-sum.js)|Medium|
+931|[Minimum Falling Path Sum](./solutions/0931-minimum-falling-path-sum.js)|Medium|
 933|[Number of Recent Calls](./solutions/0933-number-of-recent-calls.js)|Easy|
 937|[Reorder Data in Log Files](./solutions/0937-reorder-data-in-log-files.js)|Medium|
 966|[Vowel Spellchecker](./solutions/0966-vowel-spellchecker.js)|Medium|

solutions/0931-minimum-falling-path-sum.js

@@ -0,0 +1,34 @@
+/**
+ * 931. Minimum Falling Path Sum
+ * https://leetcode.com/problems/minimum-falling-path-sum/
+ * Difficulty: Medium
+ *
+ * Given an n x n array of integers matrix, return the minimum sum of any falling path
+ * through matrix.
+ *
+ * A falling path starts at any element in the first row and chooses the element in the
+ * next row that is either directly below or diagonally left/right. Specifically, the
+ * next element from position (row, col) will be (row + 1, col - 1), (row + 1, col),
+ * or (row + 1, col + 1).
+ */
+
+/**
+ * @param {number[][]} matrix
+ * @return {number}
+ */
+var minFallingPathSum = function(matrix) {
+  let previousRow = [...matrix[0]];
+
+  for (let row = 1; row < matrix.length; row++) {
+    const currentRow = new Array(matrix.length);
+    for (let col = 0; col < matrix.length; col++) {
+      const leftDiagonal = col > 0 ? previousRow[col - 1] : Infinity;
+      const directlyAbove = previousRow[col];
+      const rightDiagonal = col < matrix.length - 1 ? previousRow[col + 1] : Infinity;
+      currentRow[col] = matrix[row][col] + Math.min(leftDiagonal, directlyAbove, rightDiagonal);
+    }
+    previousRow = currentRow;
+  }
+
+  return Math.min(...previousRow);
+};