Codeforces976E Well played! 【贪心】

题目分析：

　　由于乘二的收获很大，所以我们可以证明乘的数一定是同一个，接着排序后依次选取，判断一下即可。

题目代码：

 #include<bits/stdc++.h>
 using namespace std;

 const int maxn = ;

 int n,a,b;

 struct node{
     int hp,dm;
 }d[maxn];

 int cmp(node alpha,node beta){
     return alpha.hp-alpha.dm > beta.hp-beta.dm;
 }

 void read(){
     scanf("%d%d%d",&n,&a,&b);
     for(int i=;i<=n;i++) scanf("%d%d",&d[i].hp,&d[i].dm);
     sort(d+,d+n+,cmp);
 }

 void work(){
     int hh = ;
     long long ext = ,ans = ;
     for(int i=;i<=a;i++) hh *= ;
     int pt;
     for(pt=;pt<=min(b,n);pt++){
     if(d[pt].hp-d[pt].dm <= ) break;
     ans += d[pt].hp;
     }
     for(int i=pt;i<=n;i++) ans += d[i].dm;
     long long em = ans;ext = ans;pt--;
     if(b == ){printf("%lld",ext);return;}
     for(int i=;i<=n;i++){
     em = ans;
     if(i<=pt){
         em = em-d[i].hp+(1ll*d[i].hp*hh);
         ext = max(ext,em);
     }else{
         if(pt < b){
         em = em+(1ll*d[i].hp*hh)-d[i].dm;
         ext = max(ext,em);
         }else{
         em = em-d[pt].hp+(1ll*d[i].hp*hh)-d[i].dm+d[pt].dm;
         ext = max(ext,em);
         }
     }
     }
     printf("%lld",ext);
 }

 int main(){
     read();
     work();
     return ;
 }