hdu 2689

OJ

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <map>
#include <set>
#include <string>
#include <cstring>
#include <list>
#include <queue>
#include <stack>
#include <cmath>

using namespace std;

#define PF(x) (scanf("%d",&x))
#define PT(x,y) (scanf("%d%d",&x,&y))
#define PR(x) (printf("%d\n",(x)))
#define PRT(x,y)(printf("%d %d\n",x,y))
#define M 1005

int arr[M];
int n,m;

int maxx(int x,int y)
{
	return x>y?x:y;
}
int minx(int x,int y)
{
	return x>y?y:x;
}
int low(int x)
{
	return x&(-x);
}
void add(int x,int c)
{
	for(x;x<M;x+=low(x))
			arr[x]+=c;
}
int sums(int x)
{
	int sumt = 0;
	for(;x;x-=low(x))
			sumt += arr[x];
	return sumt;
}

void init()
{
	int q;
	while(scanf("%d",&n)!=EOF)
	{
		memset(arr,0,sizeof(arr));
	    int ans = 0;

		for(int i=0;i<n;i++)
		{
			int x;
			PF(x);
			ans += sums(x);
			add(x,1);
		}
		PR(n*(n-1)/2-ans);
		
	}
	return ;
}
int main()
{
	init();
	return 0;
}