洛谷P2345 奶牛集会
洛谷P2345 奶牛集会
树状数组
按 v 从小到大排序 消除 max 影响
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 }
