[P2657]低头一族

原题链接

树状数组
这个题的题解到处都是啦
安利一下同学的讲解某不愿意透露姓名的绅士

#include<iostream>#include<cstring>#include<algorithm>#include<cstdio>#include<cmath>#include<queue>#include<vector>#include<climits>#include<string>#include<cstdlib>#include<ctime>#define LL long long#define MOD 1000000007#define pi 3.141592653589using namespace std;struct nico{    LL v,x;}cow[200005];LL n,maxn,s,sp,cnt,ans,sum[200005],tot[200005];void add(int p,int w){    for(LL i=p;i<=maxn;i+=(i&-i))    {        sum[i]++;        tot[i]+=w;          }}void ask(int p){    for(LL i=p;i>0;i-=(i&-i))    {        cnt+=sum[i];        sp+=tot[i];    }}bool comp(nico a,nico b){    return a.v<b.v;}int main(){    LL i;    scanf("%lld",&n);    for(i=1;i<=n;i++)    {        scanf("%lld%lld",&cow[i].v,&cow[i].x);        maxn=max(cow[i].x,maxn);            }    sort(cow+1,cow+n+1,comp);    for(i=1;i<=n;i++)    {        s+=cow[i].x;        sp=0;        cnt=0;        add(cow[i].x,cow[i].x);        ask(cow[i].x);        ans+=(cnt*cow[i].x-sp)*cow[i].v;        cnt=i-cnt;        sp=s-sp;        ans+=(sp-cnt*cow[i].x)*cow[i].v;            }    printf("%lld",ans);    return 0;}