Friend
Time Limit: 1000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1994 Accepted Submission(s): 1003
Problem Description
Friend number are defined recursively as follows.
(1) numbers 1 and 2 are friend number;
(2) if a and b are friend numbers, so is ab+a+b;
(3) only the numbers defined in (1) and (2) are friend number.
Now your task is to judge whether an integer is a friend number.
Input
There are several lines in input, each line has a nunnegative integer a, 0<=a<=2^30.
Output
For the number a on each line of the input, if a is a friend number, output “YES!”, otherwise output “NO!”.
Sample Input
Sample Output
Source
解题思路：参考题解
#include<stdio.h>
int main()
{
int n;
while(scanf("%d",&n)!=EOF)
{
if(n==0){
printf("NO!\n");
continue;}
n++;
while(n)
{
if(n%2==0)
n/=2;
else
break;
}
while(n)
{
if(n%3==0)
n/=3;
else
break;
}
if(n==1)
printf("YES!\n");
else
printf("NO!\n");
}
return 0;
}
friend（杭电1719）
原文：http://blog.csdn.net/hdd871532887/article/details/44539049
