汉堡汉堡汉题解

学生版：

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll t[51],p[51];
ll c(int n,ll x) {
    if(n==0) {
        return 1;
    }
    if(x==1) {
        return 0;
    }else if(x<=t[n-1]+1) {
        return c(n-1,x-1);
    }else if(x==t[n-1]+2) {
        return p[n-1]+1;
    }else if(x<=t[n-1]*2+2) {
        return p[n-1]+1+c(n-1,x-(t[n-1]+2));
    }else{
        return p[n];
    }
}
int main()
{
    t[0]=1;
    p[0]=1;
    for(int i=1;i<=50;i++) {
        t[i]=2*t[i-1]+3;
        p[i]=2*p[i-1]+1;
    }
    int n;
    ll x;
    cin>>n>>x;
    cout<<c(n,x)<<endl;
    return 0;
}

老师版：

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
ll t[51],p[51];
ll count(int n,ll x) {
    if(n==0) {
        return 1;
    }
    if(x==1) {
        return 0;
    }else if(x<=t[n-1]+1) {
        return count(n-1,x-1);
    }else if(x==t[n-1]+2) {
        return p[n-1]+1;
    }else if(x<=t[n-1]*2+2) {
        return p[n-1]+1+count(n-1,x-(t[n-1]+2));
    }else{
        return p[n];
    }
}
int main()
{
    t[0]=1;
    p[0]=1;
    for(int i=1;i<=50;i++) {
        t[i]=2*t[i-1]+3;
        p[i]=2*p[i-1]+1;
    }
    int n;
    ll x;
    cin>>n>>x;
    cout<<count(n,x)<<endl;
    return 0;
}