题解

#include<iostream>
#include<queue>
using namespace std;
int tn[4][2]={-1,0,0,-1,1,0,0,1};
struct loc{int x,y;};
struct Node{int x,y,turn;loc tmp;}t;
int main(){
    int m,n;
    while(cin>>n>>m){
        if(!n) return 0;
        int a[1001][1001],qu,a1,b1,a2,b2;
        for(int i=1;i<=n;i++) {
            for(int j=1;j<=m;j++) {
                cin>>a[i][j];
            }
        }
        cin>>qu;
        while(qu--){
            cin>>a1>>b1>>a2>>b2;
            string ans="NO\n";
            if(a[a1][b1]!=a[a2][b2]||a[a1][b1]==0||a[a2][b2]==0) {cout<<ans;continue;}
            queue<Node>q;
            q.push({a1,b1,0,{a1,b1}});
            while(q.size()){
                t=q.front();
                q.pop();
                if(t.x==a2&&t.y==b2) {
                    ans="YES\n";
                    break;
                }
                for(int i=0;i<4;i++){
                    int nx=t.x+tn[i][0],ny=t.y+tn[i][1];
                    if(nx>0&&nx<=n&&ny>0&&ny<=m&&(!a[nx][ny]||a[nx][ny]==a[a2][b2])){
                        if(nx==t.x&&t.tmp.x==nx||ny==t.y&&t.tmp.y==ny) q.push({nx,ny,t.turn,{t.x,t.y}});
                        else {q.push({nx,ny,t.turn+1,{t.x,t.y}});}
                    }
                }
            }
            if(t.turn>2)cout<<"NO\n";
            else cout<<ans;
        }
    }
}