Longest Increasing Path in a Matrix LeetCode solution in JavaScript

1
var longestIncreasingPath = function (matrix) {
2
  const m = matrix.length,
3
    n = matrix[0].length;
4
  const dp = new Array(m).fill(0).map(() => {
5
    return new Array(n).fill(-1);
6
  });
7

8
  let ans = 0;
9
  const dir = [0, -1, 0, 1, 0];
10

11
  const dfs = (x, y) => {
12
    if (dp[x][y] != -1) return dp[x][y];
13

14
    for (let i = 1; i <= 4; i++) {
15
      const [nx, ny] = [x + dir[i], y + dir[i - 1]];
16
      if (
17
        nx >= 0 &&
18
        ny >= 0 &&
19
        nx < m &&
20
        ny < n &&
21
        matrix[nx][ny] > matrix[x][y]
22
      ) {
23
        dp[x][y] = Math.max(dp[x][y], 1 + dfs(nx, ny));
24
      }
25
    }
26

27
    if (dp[x][y] == -1) dp[x][y] = 1;
28
    ans = Math.max(ans, dp[x][y]);
29
    return dp[x][y];
30
  };
31

32
  for (let i = 0; i < m; i++) {
33
    for (let j = 0; j < n; j++) {
34
      if (dp[i][j] == -1) dfs(i, j);
35
    }
36
  }
37

38
  return ans;
39
};