题解 | #矩阵最长递增路径#

import java.util.*;
public class Solution {
    int maxStep = 0;
    public int solve (int[][] matrix) {
        //因为不知道起始点，所以所有的点都要试一遍
        for (int i = 0; i < matrix.length; i++) {
            for (int j = 0; j < matrix[0].length; j++) {
                count(1,i,j,matrix,-1);
            }
        }
        return maxStep;
    }

    private void count( int steps,int i, int j, int[][] matrix, int last){
        //边界判定，以及小于上一个值的也属于走不通的
        if (i < 0 || i >= matrix.length
        || j < 0 || j >= matrix[0].length
        || matrix[i][j] <= last) return;
        //记录备份当前值
        int cur = matrix[i][j];
        //将走过的路涂黑，这里就是变成-1
        matrix[i][j] = -1;
        maxStep = Math.max(steps, maxStep);
        //向下
        count(steps + 1, i+ 1, j, matrix, cur);
        //向上
        count(steps + 1,i - 1, j, matrix, cur);
        //向右
        count(steps + 1,i, j + 1, matrix, cur);
        //向左
        count(steps + 1,i, j - 1, matrix, cur);
      
        //走完上面以后说明要回退了，重新给这个点赋值回去
        matrix[i][j] = cur;
    }
}