矩阵中的路径

private int[][] next = {{0, -1}, {0, 1}, {-1, 0}, {1, 0}};
private int cols;
private int rows;
public boolean hasPath(char[] matrix, int rows, int cols, char[] str){
    if (rows == 0 || cols == 0){
        return false;
    }
    this.rows = rows;
    this.cols = cols;
    boolean[][] marked = new boolean[rows][cols];
    char[][] chars = buildMatrix(matrix);
    for (int i = 0; i < rows; i++){
        for (int j = 0; j < cols; j++){
            if (backing(chars, str, marked, 0, i, j)){
                return true;
            }
        }
    }
    return false;
}
private boolean backing(char[][] chars, char[] str, boolean[][] marked, int pathLen, int r, int c){
    if (pathLen == str.length){
        return true;
    }
    if (r < 0 || r >= rows || c < 0 || c >= cols || chars[r][c] != str[pathLen] || marked[r][c]){
        return false;
    }
    marked[r][c] = true;
    for (int[] n : next){
        if (backing(chars, str, marked, pathLen + 1, r + n[0], c + n[1])){
            return true;
        }
    }
    marked[r][c] = false;
    return false;
}
private char[][] buildMatrix(char[] chars){
    char[][] matrix = new char[rows][cols];
    for (int i = 0, idx = 0; i < rows; i++){
        for (int j = 0; j < cols; j++){
            matrix[i][j] = chars[idx++];
        }
    }
    return matrix;
}