hdu 5491 The Next （位运算）

#include<stdio.h>
#include<string.h>
#include<math.h>
#include<stdlib.h>
#include<algorithm>

const int N = 110;
typedef long long ll;

using namespace std;

int d[N];

int get(ll n)
{
    int j = 0, num = 0;
    while(n)
    {
        d[j++] = n % 2;
        if(n % 2 == 1)
            num++;
        n /= 2;
    }
    return num;
}//求n的二进制中1的个数

ll Pow(int a, int b)
{
    ll ans = 1;
    while(b)
    {
        if(b % 2 == 1)
            ans *= a;
        a *= a;
        b /= 2;
    }
    return ans;
}//快数幂求a的b次幂

int main()
{
    int t, num, a, b, x = 0;
    ll n;
    scanf("%d", &t);
    while(t--)
    {
        x++;
        scanf("%I64d%d%d", &n, &a, &b);
        memset(d, 0, sizeof(d));
        n++;
        num = get(n);
        printf("Case #%d: ", x);
        while(1)
        {
            if(num >= a && num <= b)
            {
                printf("%I64d\n", n);
                break;
            }
            else if(num < a)
            {
                int k = 0;
                while(d[k])
                    k++;
                d[k] = 1;
                n += Pow(2, k);
                num++;
            }
            else if(num > b)
            {
                int k = 0;
                while(!d[k])
                    k++;
                n += Pow(2, k);
                num = get(n);
            }
        }
    }
    return 0;
}