ugly-numbers

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 noinput to this program. Output should consist of a single line asshown below, with <number> replaced by the number computed.

Sample output
The 1500’th ugly number is <number>.

法1

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#include <iostream>
#include <set>

using namespace std;

int main() {
    set<int> s{1};
    for(set<int>::iterator i = s.begin();i!=s.end();i++)
    {
        s.insert((*i)*2);
        s.insert((*i)*3);
        s.insert((*i)*5);
        if(s.size()>=1670)
            break;
    }
    set<int>::iterator i = s.begin();
    advance(i,1499);
    cout<<"The 1500'th ugly number is "<<*i<<'.'<<endl;
    return 0;
}