joj1751

 1751: Ugly Numbers

Result	TIME Limit	MEMORY Limit	Run Times	AC Times	JUDGE
	3s	8192K	1168	351	Standard

Ugly numbers are numbers whose only prime factors are 2, 3 or 5. The sequence

1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, ...

shows the first 11 ugly numbers. By convention, 1 is included.

Write a program to find and print the 1500'th ugly number.

Input and Output

There is no input to this program. Output should consist of a single line as shown below, with <number> replaced by the number computed.

Sample output

The 1500'th ugly number is <number>.

This problem is used for contest: 112 

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Problem Set with Online Judge System Version 3.12
Jilin University

Developed by skywind, SIYEE

这个这个题目实际上是一个优先队列的应用问题，每次都从队列当中取出最小的数字然后分别乘以2,3,5再放入队列当中。

注意这个题目的输出格式，不能包括<>

#include<iostream>
#include<queue>
#include<stdio.h>
using namespace std;
class cmp
{
    public:
    bool operator()(const long long  &a,const long long &b)
    {
        return a>b;
    }
};
int main()
{
    //freopen("out.txt","w",stdout);
    priority_queue<long long ,vector<long long>,cmp>q;
    q.push(1);
    int n=1;
    while(n<1500)
    {
        long long  t=q.top();
        q.pop();
       // cout<<t<<endl;
        while(!q.empty()&&t==q.top())q.pop();
        q.push(t*2);
        q.push(t*3);
        q.push(t*5);
        n++;
    }
    cout<<"The 1500'th ugly number is "<<q.top()<<"."<<endl;
    return 0;
}