题解 | #矩阵最长递增路径#

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     * 递增路径的最大长度
     * @param matrix int整型二维数组 描述矩阵的每个数
     * @return int整型
     */
    int maxLength = 0;
    public int solve (int[][] matrix) {
        // write code here
        int m = matrix.length;
        if(m == 0){
            return 0;
        }
        int n = matrix[0].length;
        int length = 0;
        for(int i = 0;i<m;i++){
            for(int j = 0;j<n;j++){
                backTrack(matrix,i,j,0);
            }
        }
        return maxLength;
    }
    private void backTrack(int[][] matrix,int i,int j,int length){
        if(++length > maxLength){
            maxLength = length;
        }
        int m = matrix.length;
        int n = matrix[0].length;
        if((j+1<n) && (matrix[i][j] < matrix[i][j+1])){
            maxLength = Math.max(length,maxLength);
            backTrack(matrix,i,j+1,length);
        }
        if(i+1<m&&matrix[i][j]<matrix[i+1][j]){
            maxLength = Math.max(length,maxLength);
            backTrack(matrix,i+1,j,length);
        }
        if(j-1>=0&&matrix[i][j]<matrix[i][j-1]){
            maxLength = Math.max(length,maxLength);      
            backTrack(matrix,i,j-1,length);
        }
        if(i-1>=0&&matrix[i][j]<matrix[i-1][j]){
            maxLength = Math.max(length,maxLength);         
            backTrack(matrix,i-1,j,length);
        }
    }
}