矩阵中的路径

    public boolean hasPath(char[] matrix, int rows, int cols, char[] str)
    {
        int[] flags=new int[matrix.length]; //用1标志走过
        for(int i=0;i<rows;i++){
            for(int j=0;j<cols;j++){
                boolean res = helper(matrix, rows, cols, i, j, 0, str, flags);
                if (res) return true;
            }
        }
        return false;
    }
    //k指当前匹对的字串下标
    public boolean helper(char[]matrix,int rows,int cols,int i,int j,int k,char[]str,int[]flag){
        int curr=i*cols+j;
        if (i<0||i>=rows||j<0||j>=cols||flag[curr]==1||matrix[curr]!=str[k]) return false;
        if (k==str.length-1) return true;

        flag[curr]=1;

        if (helper(matrix,rows,cols,i+1,j,k+1,str,flag)||helper(matrix,rows,cols,i-1,j,k+1,str,flag)||
                helper(matrix,rows,cols,i,j+1,k+1,str,flag)||helper(matrix,rows,cols,i,j-1,k+1,str,flag)
        )return true;

        flag[curr]=0;
        return false;
    }