hdu 2838 Cow Sorting

/************************************************
* By: chenguolin                               *
* Date: 2013-08-21                             *
* Address: http://blog.csdn.net/chenguolinblog *
***********************************************/
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;

typedef __int64 int64;
const int MAXN = 100010;

int n , num[MAXN];
int64 treeNum[MAXN];
int64 treeSum[MAXN];

int lowbit(int x){
return x&(-x);
}

int64 getSum(int x , int64 *arr){
int64 sum = 0;
while(x){
sum += arr[x];
x -= lowbit(x);
}
return sum;
}

void add(int x , int val , int64 *arr){
while(x < MAXN){
arr[x] += val;
x += lowbit(x);
}
}

int64 solve(){
memset(treeNum , 0 , sizeof(treeNum));
memset(treeSum , 0 , sizeof(treeSum));
int64 ans = 0;
int64 total = 0;
for(int i = 1 ; i <= n ; i++){
if(i > 1){
ans += total-getSum(num[i]-1 , treeSum);
ans += (i-1-getSum(num[i]-1 , treeNum))*num[i];
}
total += num[i];
add(num[i] , 1 , treeNum);
add(num[i] , num[i] , treeSum);
}
return ans;
}

int main(){
while(scanf("%d" , &n) != EOF){
for(int i = 1 ; i <= n ; i++)
scanf("%d" , &num[i]);
printf("%I64dd\n" , solve());
}
return 0;
}