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 = 320000;

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=1;i<=n;i++) scanf("%d%d",&d[i].hp,&d[i].dm);
    sort(d+1,d+n+1,cmp);
}

void work(){
    int hh = 1;
    long long ext = 0,ans = 0;
    for(int i=1;i<=a;i++) hh *= 2;
    int pt;
    for(pt=1;pt<=min(b,n);pt++){
    if(d[pt].hp-d[pt].dm <= 0) 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 == 0){printf("%lld",ext);return;}
    for(int i=1;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 0;
}