poj 1338 Ugly Numbers

Ugly Numbers

Time Limit: 1000MS		Memory Limit: 10000K
Total Submissions: 21649		Accepted: 9680

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

1
2
9
0

Sample Output

1
2
10

由题意可知这个数一定是2或3或5的倍数则每次取这三个数的倍数中最小的那个即可
注意：数据范围超过了int型  应该使用long long或者int_64

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#include<stdio.h> #include<string.h> #define MAX 1510 #define min(x,y)(x<y?x:y) long long ugly[MAX]; int main() {     int n,m,j,i;     int a,b,c;     int u2,u3,u5;     u2=1;u3=1;u5=1;     ugly[1]=1;     for(i=2;i<MAX;i++)     {         a=2*ugly[u2];         b=3*ugly[u3];         c=5*ugly[u5];         ugly[i]=min(a,min(b,c));         if(ugly[i]==a) u2++;         if(ugly[i]==b) u3++;         if(ugly[i]==c) u5++;     }     while(scanf("%d",&n),n)     {         printf("%d\n",ugly[n]);     }     return 0; }