LeetCode:Longest Increasing Path in a Matrix

Longest Increasing Path in a Matrix

Total Accepted: 15060  Total Submissions: 46586  Difficulty: Hard

Given an integer matrix, find the length of the longest increasing path.

From each cell, you can either move to four directions: left, right, up or down. You may NOT move diagonally or move 

outside of the boundary (i.e. wrap-around is not allowed).

Example 1:

nums = [
  [9,9,4],
  [6,6,8],
  [2,1,1]
]

Return 4
The longest increasing path is [1, 2, 6, 9].

Example 2:

nums = [
  [3,4,5],
  [3,2,6],
  [2,2,1]
]

Return 4
The longest increasing path is [3, 4, 5, 6]. Moving diagonally is not allowed.

Credits:
Special thanks to @dietpepsi for adding this problem and creating all test cases.

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思路：

DFS.

java code:

public class Solution {
    
    public int longestIncreasingPath(int[][] matrix) {
        
        if(matrix == null || matrix.length == 0) return 0;
        int rows = matrix.length;
        int cols = matrix[0].length;
        
        int[][] maxLen = new int[rows][cols];
        
        int ans = 1;
        for(int i=0;i= rows || y < 0 || y >= cols) continue;
            if(matrix[i][j] <= matrix[x][y]) continue;
            
            max = Math.max(max, 1 + DFS(matrix, maxLen, x, y, rows, cols));
        }
        maxLen[i][j] = max;
        return max;
    }
    
    
}