Gym - 100519I [NONE]

题目链接:https://vjudge.net/problem/Gym-100519I

解题思路:

先挂在这里

#include<bits/stdc++.h>
#define inf 0x3f3f3f3f
using namespace std;
typedef long long ll;
const int mx = 3e5+10;
bool vis[mx];
int top,pri[mx];
void init(){
	for(int i=2;i<mx;i++){
		if(!vis[i]) pri[top++] = i;
		for(int j=0;j<top&&pri[j]*i<mx;j++)
		{
			vis[pri[j]*i] = 1;
			if(i%pri[j]==0) break;
		}
	}
}
char buff[100];
int res[100];
bool check(ll P){
	int l = 1,r = P - 1;
	if(res[0]) r = (P-1)/2;
	else l = (P+1)/2;
	ll m = 2,L,R,t;
	for(int i=1;i<41;i++,m<<=1){
		L = l * m,R = r * m,t = L / P;
		L -= t*P,R -= t*P;
		if(res[i]) R = min(R,(P-1)/2);
		else L = max(L,(P+1)/2);
		L += t*P,R += t*P;
		l = (L-1) / m + 1,r = R / m;
		if(l>r) return 0; 
	}
	return 1;
}
int main(){
	init();
	int n;scanf("%d",&n);
	for(int i=0;i<41;i++){
		puts("2");
		fflush(stdout);
		scanf("%s",buff);
		if(buff[0]=='O'){
			return 0;
		}
		res[i] = buff[0] == '>';
	}
	for(int i=0;i<top;i++)
	if(check(pri[i])){
		printf("%d\n",pri[i]);
		fflush(stdout);
		break;
	}
	return 0;
}