http://acm.hdu.edu.cn/showproblem.php?pid=1394
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<math.h>
#include<iostream>
#include<algorithm>
using namespace std;
const int sizen=100000;
int a[sizen],b[sizen],c[sizen];
int t;
int num;
void Merge(int x,int Mid,int y)
{
int i,j;
i=x;
j=Mid+1;
t=i;
while(i<=Mid&&j<=y)
{
if(a[i]<a[j])
b[t++]=a[i++];
else
b[t++]=a[j++],num+=(Mid-i+1);
}
while(i<=Mid)
b[t++]=a[i++];
while(j<=y)
b[t++]=a[j++];
for(i=x;i<=y;i++)
a[i]=b[i];
}
void merge_sort(int x,int y)
{
if(x==y)
return;
int Mid=(x+y)>>1;
merge_sort(x,Mid);
merge_sort(Mid+1,y);
Merge(x,Mid,y);
}
int main()
{
int n;
int i;
while(scanf("%d",&n)!=EOF)
{
num=0;
memset(a,0,sizeof(a));
memset(b,0,sizeof(b));
for(i=1;i<=n;i++)
{
scanf("%d",&a[i]);
c[i]=a[i];
}
merge_sort(1,n);
int ans=num;
for(i=1;i<n;i++)
{
num-=c[i];
num+=(n-1-c[i]);
if(ans>num)
ans=num;
}
printf("%d\n",ans);
}
return 0;
}
