UVA-12627

一个简单的递归，注意边界条件以及开 LONG LONG !!!

#include<bits/stdc++.h>
using namespace std;
typedef  long long ll;
ll func(ll k, ll i){
    if(i==0) return 0;
    if(k==0) return 1;
    ll sum= (int)pow(2,k);
    if(i>sum/2){
        return 2*pow(3,k-1)+func(k-1,i-sum/2);
    }
    else{
        return 2*func(k-1,i);
    }
}
int main(void){
    ll t;
    cin>>t;
    for(int i=1;i<=t;i++){
        ll k,a,b;
        cin>>k>>a>>b;
        printf("Case %d: %lld\n",i,func(k,b)-func(k,a-1));
    }
}