Codeforces Round #417 (Div. 2) C. Sagheer and Nubian Market(二分)

题目链接：Codeforces Round #417 (Div. 2) C. Sagheer and Nubian Market

题意：

有n个物品，S的钱，买每个物品有个计算价钱的公式。

让你在S钱中买最多的物品。

题解：

二分瞎搞一下就行了。

#include<bits/stdc++.h>
#define F(i,a,b) for(int i=(a);i<=(b);++i)
using namespace std;
typedef long long ll;
const int N=1e5+7;

struct Node
{
    int a,idx;
    ll v;
    bool operator <(const Node &b)const{return v<b.v;}
}a[N];

int n,m;

int check(int mid)
{
    F(i,1,n)a[i].v=a[i].a+1ll*a[i].idx*mid;
    sort(a+1,a+1+n);
    ll an=0;
    F(i,1,mid)an+=a[i].v;
    return an<=m?an:-1;
}

int main()
{
    scanf("%d%d",&n,&m);
    F(i,1,n)scanf("%d",&a[i].a),a[i].idx=i;
    int l=1,r=n,mid,ans=0,ans2=0,tp;
    while(l<=r)
    {
        mid=l+r>>1;
        if((tp=check(mid))!=-1)ans=mid,ans2=tp,l=mid+1;
        else r=mid-1;
    }
    printf("%d %d\n",ans,ans2);
    return 0;
}