算法提高 快乐司机 贪心

http://lx.lanqiao.cn/problem.page?gpid=T321

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

const int maxn=10005;
const int INF=0x3f3f3f3f;

int n,m;
struct Node{
    int w;
    double v;
    bool operator <(Node obj) const{
        return v>obj.v;
    }
}node[maxn];



int main(){

    cin >> n >> m;

    for (int i=0;i<n;i++){
        int x;
        double y;
        cin >> x >> y;
        node[i].w=x;
        node[i].v=y/x;
    }
    sort(node,node+n);
    int i=0;
    double ans=0;
    while (m){
        if (m>=node[i].w){
            ans+=node[i].w*node[i].v;
            m-=node[i].w;
            i++;
        }
        else{
            ans+=m*node[i].v;
            m=0;
        }
    }

    printf("%.1lf",ans);
}