luogu 2878 贪心

Posted 2021-01-07 asdic

其实这题不难，只是想告诉自己：贪心不全是真的脑残拿最大就AC

此题实际上就是比较x,y优先级利用时间计算得到a[i]t/a[i].d(没错时间在上，并非惯性思维的d在上)

t*a[x].d+(t+a[x]*t)*a[y].d<=t*a[y].d+(t+a[y].t)*a[x].d分别比较不同顺序带给两者的花费

#include<bits/stdc++.h>
#define rep(i,x,y) for(register int i=x;i<=y;i++)
#define LL long long
using namespace std;
const int N=100500;
int n;LL ans,now;
inline int read(){
    int x=0,f=1;char ch=getchar();
    while(!isdigit(ch)){if(ch==‘-‘)f=-1;ch=getchar();}
    while(isdigit(ch)){x=(x<<1)+(x<<3)+(ch^48);ch=getchar();}
    return x*f;}struct node{int t,d;double k;}a[N];
bool cmp(node a,node b){return a.k<b.k;}int main(){
    n=read();rep(i,1,n) a[i].t=read()*2,a[i].d=read(),a[i].k=(double)a[i].t/a[i].d;
    sort(a+1,a+1+n,cmp);
    for(int i=1;i<=n;i++)
    ans+=now*a[i].d,now+=a[i].t;
    printf("%lld",ans);return 0;}