紫书 习题 10-7 UVa 10539（long long + 素数筛）

注意要开long long

如果int * int会炸

那么久改成long long * int

#include<cstdio>
#include<vector>
#include<cstring>
#define REP(i, a, b) for(int i = (a); i < (b); i++)
using namespace std;

typedef long long ll;
const int MAXN = 1123456;
bool is_prime[MAXN];
vector<int> prime;

void init()
{
	memset(is_prime, true, sizeof(is_prime));
	is_prime[0] = is_prime[1] = false;
	REP(i, 2, MAXN)
	{
		if(is_prime[i]) prime.push_back(i);
		REP(j, 0, prime.size())
		{
			if(i * prime[j] >= MAXN) break;
			is_prime[i * prime[j]] = false;
			if(i % prime[j] == 0) break;
		}
	}
}

int sum(ll x, int p)
{
	int ret = 0;
	ll t = (ll)p * p; //注意这里
	while(t <= x)
	{
		ret++;
		t *= p;
	}
	return ret;
}

int f(ll x)
{
	int ret = 0;
	REP(i, 0, prime.size())
	{
		if((ll)prime[i] * prime[i] > x) break;　//注意这里
		ret += sum(x, prime[i]);
	}
	return ret;
}

int main()
{
	init();
	int n;
	ll a, b;
	scanf("%d", &n);
	REP(i, 0, n)
	{
		scanf("%lld%lld", &a, &b);
		printf("%d\n", f(b) - f(a - 1));
	}
	return 0;
}