# 洛谷P2345 奶牛集会

 1 #include <bits/stdc++.h>
2 #define For(i, j, k) for(int i=j; i<=k; i++)
3 #define Dow(i, j, k) for(int i=j; i>=k; i--)
4 #define LL long long
5 using namespace std;
6 inline int read() {
7     int x = 0, f = 1;
8     char ch = getchar();
9     while(ch<'0'||ch>'9') { if(ch=='-') f = -1; ch = getchar(); }
10     while(ch>='0'&&ch<='9') { x = x*10+ch-48; ch = getchar(); }
11     return x * f;
12 }
13 void write(int x) {
14     if(x<0) putchar('-'), x = -x;
15     if(x>9) write(x/10);
16     putchar(x%10+48);
17 }
18 inline void writeln(int x) { write(x); putchar('\n'); }
19
20 const int N = 20011;
21 int n;
22 struct node{
23     int v, pos;
24 }a[N];
25 struct TT{
26     LL sum;
27     int num;
28 }tree[N];
29 LL sumpos, ans;
30
31 inline bool cmp_v(node a, node b) {
32     return a.v < b.v;
33 }
34
35 inline int lowbit(int x) { return x&(-x); }
36
37 inline void add(int pos) {
38     for(int x=pos; x<=20000; x+=lowbit(x) ) {
39         ++tree[x].num;
40         tree[x].sum += pos;
41     }
42 }
43
44 inline TT Query(int pos) {
45     TT p; p.num = 0; p.sum = 0;
46     for(int x=pos; x; x-=lowbit(x)) {
47         p.num += tree[x].num;
48         p.sum += tree[x].sum;
49     }
50     return p;
51 }
52
53 int main() {
54     n = read();
55     For(i, 1, n) {
56         a[i].v = read(); a[i].pos = read();
57     }
58     sort(a+1, a+n+1, cmp_v);
59     For(i, 1, n) {
60         TT p = Query(a[i].pos);
61         ans = ans+ a[i].v*(1ll*p.num*a[i].pos-p.sum + sumpos-p.sum-(1ll*i-1-p.num)*a[i].pos );
62         sumpos += a[i].pos;
63         add(a[i].pos);
64     }
65     printf("%lld\n", ans);
66     return 0;
67 }

posted @ 2018-02-21 10:54  third2333  阅读(241)  评论(0编辑  收藏  举报