Codeforces 75C (二分+数学)

http://codeforces.com/problemset/problem/75/C

先求两个数的所有公因数，再二分查找在不在[low,high]内即可。

不用upper_bound的AC代码：

#include <cassert>
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#if __cplusplus >= 201103L
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdalign>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
#if __cplusplus >= 201103L
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#endif
#define INF 1000000007
/*
	Problem: Modified GCD
	Source: Codeforces 75C
	Author: fts2001
*/
using namespace std;
int a,b,q,g,siz;
vector<int> cd;
int gcd(int x,int y){
	if(y)return gcd(y,x%y);
	else return x;
}
int main(){
	ios::sync_with_stdio(false);
	cin>>a>>b>>q;
	g=gcd(a,b);
	for(int i=1;i*i<=g;i++){
		if(g%i==0){
			cd.push_back(i);
			if(i!=g/i)cd.push_back(g/i);
		}
	}
	sort(cd.begin(),cd.end());
	cd.push_back(INF);
	int siz=cd.size();
	while(q--){
		int l,r;
		cin>>l>>r;
		int lb=0,ub=siz-1;
		while(ub-lb>1){
			int mid=(lb+ub)/2;
			if(cd[mid]<=r)lb=mid;
			else ub=mid;
		}
		if(cd[ub-1]>=l)cout<<cd[ub-1]<<endl;
		else cout<<-1<<endl;
	}
	return 0;
}