pipioj 1028: 可乐（贪心）

http://www.pipioj.online/problem.php?id=1028

#define IO std::ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
#define bug(x) cout<<#x<<" is "<<x<<endl
#include <bits/stdc++.h>
#define iter ::iterator
using namespace  std;
typedef long long ll;
typedef pair<int,ll>P;
#define pb push_back
#define mk make_pair
#define se second
#define fi first
#define rs o*2+1
#define ls o*2
const ll mod=1e9+7;
const int N=2e5+5;
int T,n,k;
 
ll a[35],v[35],res[35];
 
ll L;
 
struct node{
    ll x;
    int id;
}b[35];
 
bool cmp(node p,node q){
    return p.x<q.x;
}
 
int main(){
    IO;
    while(cin>>n>>L){
        for(int i=1;i<=n;i++)cin>>a[i],v[i]=(1<<(i-1)),res[i]=0;
 
        ll h=1;
        for(int i=n;i>=1;i--){
            b[i].id=i;
            b[i].x=a[i];
            b[i].x*=h;
            h*=2;
        }
 
        sort(b+1,b+1+n,cmp);
        ll ans=0,res=1e18;
        for(int i=1;i<=n;i++){
            if(L>=v[b[i].id]){
                ll x=L/v[b[i].id];
                ans+=x*a[b[i].id];
                L-=x*v[b[i].id];
            }
            if(!L)break;
            res=min(res,ans+a[b[i].id]);
        }
        ans=min(ans,res);
        cout<<ans<<endl;
    }
}