洛谷P1208 [USACO1.3]混合牛奶 Mixing Milk

题目传送门

也是十分简单的贪心，是性价比贪心，策略：优先选择单价较低的奶农买奶

#include<cstdio>
#include<iostream>
#include<algorithm>

using namespace std;

struct node
{
    int a,b;
};
node milk[5005];
int n,m,ans;

inline bool cmp(node x,node y)
{
    return x.a<y.a;
}

int main()
{
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;i++)
        scanf("%d%d",&milk[i].a,&milk[i].b);
    sort(milk+1,milk+m+1,cmp);
    for(int i=1;i<=m;i++)
    {
        if(n>=milk[i].b)
        {
            n-=milk[i].b;
            ans+=milk[i].b*milk[i].a;
        }
        else 
        {
            ans+=milk[i].a*n;
            break;
        }
    }
    printf("%d",ans);
    return 0;
}