Add solution #329

Author: JoshCrozier

Diff for: README.md

@@ -249,6 +249,7 @@
 322|[Coin Change](./0322-coin-change.js)|Medium|
 326|[Power of Three](./0326-power-of-three.js)|Easy|
 328|[Odd Even Linked List](./0328-odd-even-linked-list.js)|Medium|
+329|[Longest Increasing Path in a Matrix](./0329-longest-increasing-path-in-a-matrix.js)|Hard|
 331|[Verify Preorder Serialization of a Binary Tree](./0331-verify-preorder-serialization-of-a-binary-tree.js)|Medium|
 334|[Increasing Triplet Subsequence](./0334-increasing-triplet-subsequence.js)|Medium|
 337|[House Robber III](./0337-house-robber-iii.js)|Medium|

Diff for: solutions/0329-longest-increasing-path-in-a-matrix.js

@@ -0,0 +1,33 @@
+/**
+ * 329. Longest Increasing Path in a Matrix
+ * https://leetcode.com/problems/longest-increasing-path-in-a-matrix/
+ * Difficulty: Hard
+ *
+ * Given an m x n integers matrix, return the length of the longest increasing path in matrix.
+ *
+ * From each cell, you can either move in four directions: left, right, up, or down. You may
+ * not move diagonally or move outside the boundary (i.e., wrap-around is not allowed).
+ */
+
+/**
+ * @param {number[][]} matrix
+ * @return {number}
+ */
+var longestIncreasingPath = function(matrix) {
+  if (!matrix.length) return 0;
+  const m = matrix.length;
+  const n = matrix[0].length;
+  const cache = new Array(m).fill().map(() => new Array(n));
+  const directions = [[0, 1], [1, 0], [0, -1], [-1, 0]];
+
+  return Math.max(...new Array(m).fill().map((_, i) =>
+    new Array(n).fill().map((_, j) => dfs(i, j))).flat());
+
+  function dfs(i, j) {
+    return cache[i][j] || (cache[i][j] = 1 + Math.max(...directions.map(([di, dj]) => {
+      const [a, b] = [i + di, j + dj];
+      return a >= 0 && a < m && b >= 0 && b < n && matrix[a][b] > matrix[i][j]
+        ? dfs(a, b) : 0;
+    })));
+  }
+};