MooFest POJ

MooFest

 POJ - 1990 

 高级数据结构p203

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;
#define LL long long 
const int maxn = 20010;

LL dis[maxn], cnt[maxn];
int n; 

struct Cow{
    int v, p;
    bool operator < (const Cow& a)const{
        return v < a.v;
    }
}c[maxn];

void init(){
    memset(dis, 0, sizeof dis);
    memset(cnt, 0, sizeof cnt);
}
LL sum(int i, LL *c){
    LL res = 0;
    for(; i; i -= i & -i) res += c[i];
    return res;
}
void add(int i, int v, LL *c){
    for(; i <= maxn; i += i & -i) c[i] += v;
}
int main(){
    while(scanf("%d", &n) != EOF){
        init();
        for(int i = 1; i <= n; i++){
            scanf("%d %d", &c[i].v, &c[i].p);
        }
        sort(c + 1, c + n + 1);
        LL tot = 0, ans = 0;
        for(int i = 1; i <= n; i++){
            LL cnt1 = sum(c[i].p, cnt), sum1 = sum(c[i].p, dis);
            LL cnt2 = i - 1 - cnt1, sum2 = tot - sum1;
            ans += c[i].v * (cnt1 * c[i].p - sum1 + sum2 - cnt2 * c[i].p);
            tot += c[i].p;
            add(c[i].p, c[i].p, dis);
            add(c[i].p, 1, cnt);
        }
        printf("%lld
", ans);
    }
    return 0;
}