OJ-Problems-Source/HDOJ/4000_autoAC.cpp

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#include <stdio.h>
#include <iostream>
using namespace std;
const int N=100001;
int a, n, f[N];
__int64 ans, tmp, tmp1;
void insert(int i)
{
for(; i<=n; i+=i&(-i))
f[i] += 1;
}
int query(int i)
{
int tmp=0;
for(; i>0; i-=i&(-i))
tmp += f[i];
return tmp;
}
int main()
{
int i, cas, cas1=1;
scanf("%d", &cas);
while(cas--)
{
scanf("%d", &n);
ans = 0;
for(i=1; i<=n; i++)
f[i] = 0;
for(i=1; i<=n; i++)
{
scanf("%d", &a);
insert(a);
tmp = query(a-1);
tmp1 = (n-a)-(i-1-tmp);
ans -= tmp*tmp1;
if(tmp1>=2)
ans += tmp1*(tmp1-1)/2;
}
printf("Case #%d: %I64d\n", cas1++, ans%100000007);
}
return 0;
}