1.6.1 3n+1问题 The 3n+1 problem

思路&题解

PC/UVA 110101/100
水题。数据范围大。需要预处理。之前处理过的+处理到这个地方的

//author: CHC
//First Edit Time:	2014-01-10 18:30
//Last Edit Time:	2014-01-10 18:30
//Filename:1.cpp
#include <iostream>
#include <cstdio>
#include <string.h>
#include <queue>
#include <algorithm>
using namespace std;
long long cs[1000001]={ 0 };
int main()
{
    for(int j=1;j<1000001;j++)
    {
        int i=1;
        long long n=j;
        while(n!=1)
        {
            if(n%2)n=n*3+1;
            else n/=2;
            if(n<j)
            {
                cs[j]=cs[n]+i;
                break;
            }
            ++i;
        }
        if(!cs[j]) cs[j]=i;
    }
    int a,b,c,d;
    while(~scanf("%d%d",&c,&d))
    {
        a=c,b=d;
        if(a>b)a^=b^=a^=b;
        int maxn=cs[a],maxi=a;
        for(int i=a+1;i<=b;i++)
            if(cs[i]>maxn)
            {
                maxn=cs[i];
                maxi=i;
            }
        printf("%d %d %d\n",c,d,maxn);
    }
    return 0;
}

The 3n + 1 problem

Consider the following algorithm to generate a sequence of numbers. Start with an integer n. If n is
even, divide by 2. If n is odd, multiply by 3 and add 1. Repeat this process with the new value of n,
terminating when n = 1. For example, the following sequence of numbers will be generated for n = 22:
22 11 34 17 52 26 13 40 20 10 5 16 8 4 2 1
It is conjectured (but not yet proven) that this algorithm will terminate at n = 1 for every integer n.
Still, the conjecture holds for all integers up to at least 1, 000, 000.
For an input n, the cycle-length of n is the number of numbers generated
up to and including the 1. In the example above, the cycle length of 22 is 16. Given any two numbers i and j,
you are to determine the maximum cycle length over all numbers between i and j, including both
endpoints.

Input

The input will consist of a series of pairs of integers i and j,
one pair of integers per line. All integers will be less than 1,000,000 and greater than 0.

Output

For each pair of input integers i and j,
output i, j in
the same order in which they appeared in the input and then the maximum cycle length for integers between and including i and j.
These three numbers should be separated by one space, with all three numbers on one line and with one line of output for each line of input.

Sample Input

1 10  
100 200  
201 210  
900 1000  

Sample Output

1 10 20  
100 200 125  
201 210 89  
900 1000 174