Codeforces1023E Down or Right 【贪心】

题目分析:

从起点开始询问终点连通性，优先右走。从终点开始询问起点连通性，优先上走。

代码：

 #include<bits/stdc++.h>
 using namespace std;

 int n;

 int query(int x1,int y1,int x2,int y2){
     printf("? %d %d %d %d\n",x1,y1,x2,y2);
     fflush(stdout);
     char str[];
     scanf("%s",str);
     if(str[] == 'Y') return ;
     else return ;
     //int z; scanf("%d",&z);
     //return z;
 }

 stack<char> sta;
 vector <char> vc;
 void work(){
     int x = ,y = ;
     while(n-x+n-y > n-){
     int z = query(x,y+,n,n);
     if(z){vc.push_back('R');y++;}
     else{vc.push_back('D');x++;}
     }
     int nx = n,ny = n;
     while(nx != x || ny != y){
     int z = query(,,nx-,ny);
     if(z){sta.push('D');nx--;}
     else{sta.push('R');ny--;}
     }
     printf("! ");
     for(int i=;i<vc.size();i++) printf("%c",vc[i]);
     while(!sta.empty()){printf("%c",sta.top());sta.pop();}
 }

 int main(){
     scanf("%d",&n);
     work();
     return ;
 }