P1101 单词方阵

没看清题，说是走了一个方向不换方向，导致一开始写bfs狂WA（因为出现了一个后继对多个前驱的情况）

#include<iostream>
#include<cstring>
#include<queue>

using namespace std;

#define PII pair<int, int>
#define x first
#define y second

const int N = 110, M = 10010;

char g[N][N];
int st[N][N];
string s = "yizhong";
int n;
int dx[] = {1, 0, -1, 0, 1, -1, 1, -1}, dy[] = {0, 1, 0, -1, 1, 1, -1, -1};
vector<PII> res;

void dfs(int x, int y, int u, int k){
    if(u == s.size()){
        for(auto t : res) st[t.x][t.y] = 1;
        return;
    }
    
    if(x < 0 || y < 0 || x >= n || y >= n) return;
    if(s[u] != g[x][y]) return;
    
    res.push_back({x, y});
    
    if(u == 0)
        for(int i = 0; i < 8; i ++){
            int a = x + dx[i], b = y + dy[i];
            dfs(a, b, u + 1, i);
        }
    else
        dfs(x + dx[k], y + dy[k], u + 1, k);
        
    res.pop_back();
}


int main(){
    cin >> n;
    
    for(int i = 0; i < n; i ++) cin >> g[i];
    
    for(int i = 0; i < n; i ++)
        for(int j = 0; j < n; j ++)
            if(g[i][j] == 'y') dfs(i, j, 0, 0);
    
    for(int i = 0; i < n; i ++){
        for(int j = 0; j < n; j ++)
            if(st[i][j]) cout << g[i][j];
            else cout << '*';
        cout << endl;
    }
    
    return 0;
}