bzoj2014

题解：

按照单价排序

然后贪心

代码：

#include<bits/stdc++.h>
using namespace std;
const int N=100005;
typedef long long ll;
ll ans,m,a[N],b[N];
int n,f[N];
int cmp(int x,int y)
{
    return b[x]<b[y];
}
int main()
{
    scanf("%d%lld",&n,&m);
    for (int i=1;i<=n;i++)scanf("%lld%lld",&b[i],&a[i]),f[i]=i;
    sort(f+1,f+n+1,cmp);
    for (int i=1;i<=n;i++)
     {
         ll k=min(a[f[i]],m/b[f[i]]);
         m-=k*b[f[i]];
         ans+=k;
     }
    printf("%lld",ans); 
}