POJ 1338 Ugly Numbers

Ugly Numbers

Time Limit: 1000MS Memory Limit: 10000KTotal Submissions: 12232 Accepted: 5368

Description

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, ...
shows the first 10 ugly numbers. By convention, 1 is included.
Given the integer n,write a program to find and print the n'th ugly number.

Input

Each line of the input contains a postisive integer n (n <= 1500).Input is terminated by a line with n=0.

Output

For each line, output the n’th ugly number .:Don’t deal with the line with n=0.

Sample Input

1290

Sample Output

1210

Source

New Zealand 1990 Division I,UVA 136

题目大意：求第N个因数只为2 3 5的数   （这是什么年代留下来的题。。。- -）

题目分析：打表

代码如下：

#include <iostream>using namespace std;int min(int a,int b,int c){if(a>b)a=b;if(a>c)a=c;return a;}int main(){int n,i,j,k,a[1510],t;for(t=1;t<=5;t++)a[t]=t;for(i=3,j=k=2;t<=1505;t++){a[t]=min(a[i]*2,a[j]*3,a[k]*5);while(a[i]*2<=a[t])i++;while(a[j]*3<=a[t])j++;while(a[k]*5<=a[t])k++;}while(cin>>t,t)cout<<a[t]<<endl;return 0;}