JZ65 矩阵中的路径

解决只能走一遍的办法就是把 在遍历时把
matrix[i][j] = '.';
改为别的字母
然后再结束时改回来；
matrix[i][j] = tmp;

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
     *
     * 
     * @param matrix char字符型二维数组 
     * @param word string字符串 
     * @return bool布尔型
     */
    public boolean hasPath (char[][] matrix, String word) {
        if(word.length() == 0) return true;

        for(int i = 0;i<matrix.length;i++){
            for(int j = 0;j<matrix[0].length;j++){
                if(helper(matrix,i,j,word)) return true;
            }
        }
        return false;
    }
    public boolean helper (char[][] matrix, int i, int j, String word) {
        if(word.length() == 0) return true;
        if(i<0 || j < 0 || i >= matrix.length || j >= matrix[0].length) return false;

        if(word.charAt(0) == matrix[i][j] ){
            char tmp = matrix[i][j];
            matrix[i][j] = '.';
            boolean res = helper(matrix,i-1,j,word.substring(1,word.length())) ||
            helper(matrix,i+1,j,word.substring(1,word.length())) ||
            helper(matrix,i,j+1,word.substring(1,word.length())) ||
            helper(matrix,i,j-1,word.substring(1,word.length()));

            matrix[i][j] = tmp;
            return res;
        }
        else return false;
    }
}