题目链接： https://leetcode.cn/problems/word-search/

题意：

给定二维char数组，询问是否能够有路径来获得给定的字符数组
无法改为动态规划表

class Solution {
public:
    bool exist(vector<vector<char>>& board, string word) {
        int n=board.size();
        int m=board[0].size();
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                if(f(board,n,m,word,i,j,0)){
                    return true;
                }
            }
        }
        return false;
    }
    bool f(vector<vector<char>>&board,int n,int m,string w,int i,int j,int k){
        //basecase!
        if(k==w.size()){
            return true;
        }
        if(i<0||i>=n||j<0||j>=m||w[k]!=board[i][j])return false;
        
        //try
        bool ans=false;
        char tmp=board[i][j];
        board[i][j]='0';
        ans=f(board,n,m,w,i-1,j,k+1)||f(board,n,m,w,i+1,j,k+1)||f(board,n,m,w,i,j-1,k+1)||f(board,n,m,w,i,j+1,k+1);
        board[i][j]=tmp;
        return ans;
    }
};