UVa 136 Ugly Numbers 【STL】【priority_queue】

#include <cstdio>
#include <iostream>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <queue>
#include <set>
#include <vector>
using namespace std;
typedef long long LL;
const int coeff[3] = {2, 3, 5};
int main()
{
priority_queue<LL, vector<LL>, greater<LL> > pq; //greater使大数往后排
set<LL> s;
pq.push(1);
s.insert(1);
for(int i = 1; ; ++i)
{
LL x = pq.top(); pq.pop();//不断更新队列最小元素
if(i == 1500)//找到目标
{
cout << "The 1500'th ugly number is " << x << ".\n";
break;
}
for(int j = 0; j < 3; ++j)
{
LL x2 = x * coeff[j]; //生成新的“丑数”
if(!s.count(x2)) { s.insert(x2); pq.push(x2);}
}
}
return 0;
}