【CF1023E】Down or Right（交互，贪心）

题意：

n<=500

思路：From https://blog.csdn.net/csdnjiangshan/article/details/81813227

 #include<cstdio>
 #include<cstring>
 #include<string>
 #include<cmath>
 #include<iostream>
 #include<algorithm>
 #include<map>
 #include<set>
 #include<queue>
 #include<vector>
 #include<bitset>
 using namespace std;
 typedef long long ll;
 typedef unsigned int uint;
 typedef unsigned long long ull;
 typedef pair<int,int> PII;
 typedef vector<int> VI;
 #define fi first
 #define se second
 #define MP make_pair
 #define N      210000
 #define M      51
 #define MOD 1000000007
 #define eps 1e-8
 #define pi     acos(-1)
 #define oo     1e9

 char s[];
 int ans[N];

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

 int calc(int x1,int y1,int x2,int y2)
 {
     return abs(x1-x2)+abs(y1-y2);
 }

 int main()
 {
     int n;
     scanf("%d",&n);
     int x=,y=;
     int k=;
     while(calc(x,y,n,n)>=n)
     {
         if(y+<=n&&query(x,y+,n,n))
         {
             y++; ans[++k]='R';
         }
          else
          {
              x++; ans[++k]='D';
          }
     }
     k=*n-; x=n; y=n;
     while(calc(x,y,,)>=n)
     {
         if(x->&&query(,,x-,y))
         {
             x--; ans[--k]='D';
         }
          else
          {
              y--; ans[--k]='R';
          }
     }
     printf("! ");
     for(int i=;i<=*n-;i++) printf("%c",ans[i]);
     return ;
 }