UVA 136

 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 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>.

这题不解释了 ， 简单DP ， 记得用long long。

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>using namespace std;long long a[1505];int main(){    //freopen("in.txt" , "r" , stdin);    int n , m1 , m2 , m3;    a[1] = 1;    m1 = m2 = m3 = 1;    for(int i = 2 ; i <= 1500 ; i++)    {        a[i] = min(2 * a[m1] , min(3 * a[m2] , 5 * a[m3]));        if(a[i] == 2 * a[m1])m1++;        if(a[i] == 3 * a[m2])m2++;        if(a[i] == 5 * a[m3])m3++;    }    printf("The 1500'th ugly number is %lld.\n",a[1500]);    return 0;}