Codeforces Round #703 (Div. 2)C (二分)
https://codeforces.com/contest/1486/problem/C2
1 #define IO std::ios::sync_with_stdio(0),cin.tie(0),cout.tie(0); 2 #define bug(x) cout<<#x<<" is "<<x<<endl 3 #include <bits/stdc++.h> 4 #define iter ::iterator 5 using namespace std; 6 typedef long long ll; 7 typedef pair<int,ll>P; 8 #define pb push_back 9 #define mk make_pair 10 #define se second 11 #define fi first 12 #define rs o*2+1 13 #define ls o*2 14 const ll inf=1e18; 15 const int N=1e3+5; 16 17 int T,n,res; 18 19 int qu(int x,int y){ 20 cout<<"? "<<x<<" "<<y<<endl; 21 int z; 22 cin>>z; 23 return z; 24 } 25 26 int gao1(int L,int R){ 27 int l=L,r=R,m=L; 28 while(l<r-1){ 29 m=(l+r)/2; 30 //bug( 31 int k=qu(m,R); 32 //ans=m; 33 if(k==res)l=m; 34 else r=m; 35 } 36 cout<<"! "<<l<<endl; 37 } 38 39 int gao2(int L,int R){ 40 int l=L,r=R,m=L; 41 while(l<r-1){ 42 m=(l+r)/2; 43 int k=qu(L,m); 44 if(k==res)r=m; 45 else l=m; 46 } 47 cout<<"! "<<r<<endl; 48 } 49 50 int main(){ 51 cin>>n; 52 res=qu(1,n); 53 int res1=-1,res2=-1; 54 if(res>1)res1=qu(1,res); 55 if(res<n)res2=qu(res,n); 56 if(res1==res)gao1(1,res); 57 else gao2(res,n); 58 } 59 /* 60 5 61 3 62 3 63 5 64 3 65 66 *2 67 68 5 69 3 70 3 71 5 72 2 73 *1 74 */
