https://ac.nowcoder.com/acm/contest/332/C

C++版本一

题解：

贪心

按价值排序，从大到小取，取足为止

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
ll t,n,m,k,q;
ll ans,cnt,flag,temp;
int a[N];
int b[N];
struct node{
    ll a,b;
    bool operator <(const node &S)const{
        return b>S.b;
    }
}e[N];
char str;
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    scanf("%lld%lld",&n,&m);
    //scanf("%d",&t);
    //while(t--){}
    for(int i=1;i<=m;i++)
        scanf("%lld",&e[i].a);
    for(int i=1;i<=m;i++)
        scanf("%lld",&e[i].b);
    ans=0;
    sort(e+1,e+m+1);
    for(int i=1;i<=m;i++){
        if(e[i].a>0&&n){
            if(e[i].a<=n){
                ans+=e[i].a*e[i].b;
                n-=e[i].a;
                e[i].a=0;
            }else{
                ans+=n*e[i].b;
                break;
            }
        }
    }
    cout << ans << endl;
    //cout << "Hello world!" << endl;
    return 0;
}