luogu P2345 奶牛集会

二次联通门 : luogu P2345 奶牛集会

 

 

 

 

/*
    luogu P2345 奶牛集会
    
    权值线段树
    
    以坐标为下标， 坐标为值建立线段树 

    对奶牛按听力由小到大排序
    
    对于要查的牛 
    每次第i次放入奶牛起作用的v就是vi；

　　每次ans+=（xi*sum-sumxl）*vi+（sumxr-xi*sum）*vi

*/
#include <algorithm>
#include <cstdio>

#define Max 400003

void read (int &now)
{
    now = 0;
    register char word = getchar ();
    while (word < '0' || word > '9')
        word = getchar ();
    while (word >= '0' && word <= '9')
    {
        now = now * 10 + word - '0';
        word = getchar ();
    }
}

inline int min (int a, int b)
{
    return a < b ? a : b;
}

inline int max (int a, int b)
{
    return a > b ? a : b;
}

inline int abs (int a)
{
    return a > 0 ? a : -a;
}

struct Segment_Tree_Data
{
    Segment_Tree_Data *Left, *Right;
    
    int l, r;
    int key;
    int Mid;
    int Count;
    
    Segment_Tree_Data ()
    {
        Mid = 0;
        Left = Right = NULL;
        key = 0;
        Count = 0;
    }
}
*Root;

class Segment_Tree_Type
{
    public :
        
        void Build (Segment_Tree_Data *&now, int l, int r)
        {
            now = new Segment_Tree_Data ();
            now->l = l;
            now->r = r;
            if (l == r)
                return ;
            now->Mid = l + r >> 1;
            Build (now->Left, l, now->Mid);
            Build (now->Right, now->Mid + 1, r);
        }
        
        void Updata (Segment_Tree_Data *&now, int pos, int to)
        {
            if (now->l == now->r)
            {
                now->key += to;
                now->Count++;
                return ;
            }
            if (pos <= now->Mid)
                Updata (now->Left, pos, to);
            else
                Updata (now->Right, pos, to);
            now->key = now->Left->key + now->Right->key;
            now->Count = now->Left->Count + now->Right->Count;
        }
        
        int Query (Segment_Tree_Data *&now, int l, int r)
        {
            if (l <= now->l && r >= now->r)
                return now->key;
            int res = 0;
            if (l <= now->Mid)
                res += Query (now->Left, l, min (now->Mid, r));
            if (r > now->Mid)
                res += Query (now->Right, max (now->Mid + 1, l), r);
            return res;
        }
        
        int Query_number_Count (Segment_Tree_Data *&now, int l, int r)
        {
            if (l <= now->l && r >= now->r)
                return now->Count;
            int res = 0;
            if (l <= now->Mid)
                res += Query_number_Count (now->Left, l, min (now->Mid, r));
            if (r > now->Mid)
                res += Query_number_Count (now->Right, max (now->Mid + 1, l), r);
            return res;
        }
};

int N;

Segment_Tree_Type Tree;

struct Cow_Data
{
    int pos;
    int value;
    
    bool operator < (const Cow_Data &now) const
    {
        return now.value > value;
    }
    
};

Cow_Data cow[Max];

int main (int argc, char *argv[])
{
    read (N);
    int pos, Value;
    long long Answer = 0;
    Tree.Build (Root, 0, Max);
    for (int i = 1; i <= N; i++)
    {
        read (cow[i].value);
        read (cow[i].pos);
    }
    std :: sort (cow + 1, cow + 1 + N);
    Tree.Updata (Root, cow[1].pos, cow[1].pos); 
    for (int i = 2; i <= N; i++)
    {
        Tree.Updata (Root, cow[i].pos, cow[i].pos);
        register long long now =  Tree.Query_number_Count (Root, 1, cow[i].pos - 1);
        Answer += (long long) cow[i].value * (cow[i].pos * now - Tree.Query (Root, 0, cow[i].pos - 1));
        Answer += (long long) cow[i].value * (Tree.Query (Root, cow[i].pos + 1, Max) - cow[i].pos * (i - now - 1));
    }
    
    printf ("%lld", Answer);
    return 0;
}