前言
牛逼构造题。
思路
代码
#include <iostream>
#include <cstdio>
#include <stack>
using namespace std;
bool query(int x, int y)
{
cout << "? " << x - 1 << ' ' << y - 1 << endl;
char ans; cin >> ans; return (ans == 'Y');
}
int a, b, n; bool zlt[114514];
void answer()
{
cout << "! "; for (int i = 1; i <= n; i++) cout << zlt[i];
cout << endl;
}
int main()
{
cin >> a >> b, n = a + b;
if (a <= b) {puts("Impossible"); return 0;}
stack <int> stk;
for (int i = 1; i <= n; i++)
if (stk.empty()) stk.push(i);
else
{
int top = stk.top();
stk.push(i);
if (!query(top, i)) stk.pop(), stk.pop(); //把这两个都丢出去
}
int good = stk.top(); //好人
for (int i = 1; i <= n; i++) zlt[i] = query(good, i);
answer();
return 0;
}
希望能帮助到大家！