Leetcode 79. 单词搜索

#include <vector>
class Solution {
public:
    int n,m;
    //标记是否被访问过
    vector<vector<bool>> visit;

    // idx（不包括）之前的都已经被访问过了
    bool dfs(int i,int j,vector<vector<char>>& board, int idx, string word)
    {
        if(idx == word.size())
            return true;
        
        // 判断先决条件
        if(i<0 || j<0 || i>=n || j>=m || visit[i][j] || word[idx]!=board[i][j])
            return false;
        
        visit[i][j]=true;
        
        bool ret= dfs(i-1,j,board,idx+1,word) || dfs(i+1,j,board,idx+1,word) || dfs(i,j-1,board,idx+1,word) || dfs(i,j+1,board,idx+1,word);
        visit[i][j] = false;
        return ret;
    }
    
    bool exist(vector<vector<char>>& board, string word) {
        // 条件判断
        n= board.size();
        if(n==0)
            return false;
        m= board[0].size();
        if (m==0)
            return false;
        
        visit.resize(n,vector<bool>(m, false));
        
        for(int i=0; i<n; ++i)
        {
            for(int j=0; j<m; ++j)
            {
                if(dfs(i,j,board,0,word))
                {
                    return true;
                }       
            }
        }
        return false;
    }
};