dfs模板题

class Solution {
    public boolean hasPath(char[][] matrix, String str) {
        if(matrix == null || matrix.length == 0 || matrix[0].length == 0){
            return false;
        }
        int row = matrix.length;
        int col = matrix[0].length;
        boolean[][] visited = new boolean[row][col];
        for(int i = 0; i < row; i++){
            for(int j = 0; j < col; j++){
                if(dfs(matrix,str,0,i,j,visited)){
                    return true;
                }
            }
        }
        return false;
    }
    private boolean dfs(char[][] m,String s,int idx, int i, int j, boolean[][] visited){
        if(idx == s.length()){
            return true;
        }
        if(i < 0 || i >= m.length || j < 0 || j >= m[0].length || visited[i][j] || m[i][j] != s.charAt(idx)){
            return false;
        }
        int[][] dirs = {{-1,0},{0,1},{1,0},{0,-1}};
        visited[i][j] = true;
        for(int[] dir : dirs){
            if(dfs(m,s,idx+1,dir[0] + i,dir[1] + j,visited)){
                return true;
            }
        }
        visited[i][j] = false;
        return false;
    }

}