hdu_1032 poj_1207_The 3n+1's problem

#include<iostream>
using namespace std;

int a[1000001];


int main()
{
    int n,m,max;
    __int64 i,k;
    int cnt ;

    for(k = 1; k <= 100000; k++)
        {
            cnt = 0;
            i = k;
            while(true)
            {
                cnt++;
                if(i==1)
                    break;
                if(i%2 == 0)
                    i = i/2;
                else
                    i = 3*i +1;
            }
            a[k] = cnt; 
        }

    while(scanf("%d%d",&n,&m)!= EOF)
    {
        int tmp;
        max = 0;
        cout<<n<<' '<<m<<' ';
        if(m < n)
        {
            tmp = n;
            n = m;
            m = tmp;
        }
            
        for(i = n; i <= m; i++)
        {
            if(a[i]>max)
                max = a[i];
        }
        
        
        cout<<max<<endl;
    }
    return 0;
}

时间有点慢，递归调用的话，可以零ms 下面是别人代码，甚好，所以贴来作比较。尚需努力啊————————

#include <stdio.h>
#define SIZE 10020  //SIZE开到10010都WA，10020就AC……
int cycle[SIZE] = {0};
int get_cycle(int n){
    if(n >= SIZE) return (n%2 == 1) ? get_cycle((3*n+1)/2)+2 : get_cycle(n/2)+1;  //n超出SIZE范围时直接递归，避免越界
    else if(cycle[n] == 0) cycle[n] = (n%2 == 1) ? get_cycle((3*n+1)/2)+2 : get_cycle(n/2)+1;
    return cycle[n];
}
int main(){
    int i, j, ii, jj;  
    cycle[1] = 1;
    for(int k = 2; k < SIZE; k++)
        get_cycle(k);
    while(EOF != scanf("%d%d", &ii, &jj)){
        i = (ii < jj) ? ii : jj;
        j = ii+jj-i;
        int max = cycle[i];
        for(int k = i+1; k <= j; k++)
            max = (cycle[k] > max) ? cycle[k] : max;
        printf("%d %d %d\n", ii, jj, max);
    }
    return 0;
}