GDUFE ACM-1006

题目：http://acm.gdufe.edu.cn/Problem/read/id/1006

Hailstone HOTPO

Time Limit: 2000/1000ms (Java/Others)

Problem Description:

    The hailstone sequence is formed in the following way:

(1) If n is even, divide it by 2 to get n'
(2) If n is odd, multiply it by 3 and add 1 to get n'

It is conjectured that for any positive integer number n, the sequence will always end in the repeating cycle: 4, 2, 1, 4, 2, 1,... Suffice to say , when n == 1, we will say the sequence has ended.

Write a program to determine the largest value in the sequence for a given n.

Input:

The first line of input contains a single integer P, (1<= P <= 100000), which is the number of data set s that follow. Each data set should be processed identically and independently.

Each data set consists of a single line of input consisting of two space separated decimal integers. The first integer is the data set number. The second integer is n, (1 <= n <= 100,000), which is the starting value.

Output:

For each data set there is a single line of output consisting of the data set number, a single space, and the largest value in the sequence starting at and including n. 

Sample Input:

4
1 1
2 3
3 9999
4 100000

Sample Output:

1 1
2 16
3 101248
4 100000

思路：判断是基数还是偶数，然后按题目要求执行，判断执行后的数与执行前的数哪个比较大，把大的留下来，直到得出1，结束

难度：简单

代码：

#include<stdio.h>
int main()
{
    int n,a,b,c;
    while(scanf("%d",&n)!=EOF)
    {
        while(n--)
        {
            scanf("%d %d",&a,&b);
            c=0;
            if(b==1) c=1;
            while(b!=1)
            {
                if(b>c)
                    c=b;
                if(b%2==0)
                    b=b/2;
                else b=b*3+1;
            }
            printf("%d %d
",a,c);
        }
    }
    return 0;
}