SPOJ Problem:Inversion Count

#include<cstdio>
#include<cstring>
int a[200005],b[200005],n,t;
int i;
long long ans;
void count(int l,int r){
    int m,i,j,k;
    if (l==r)return;
    m=(l+r)>>1;
    count(l,m);count(m+1,r);
    i=l;j=m+1;k=l-1;
    while(i<=m&&j<=r){
        while(a[i]<=a[j]&&i<=m){
            b[++k]=a[i++];
            ans+=(j-m-1);
        }
        while(a[i]>a[j]&&j<=r){
            b[++k]=a[j++];
        }
    }
    while(i<=m){
        b[++k]=a[i++];
        ans+=(j-m-1);
    }
    for (i=l;i<j;i++)a[i]=b[i];
}
int main(){
    scanf("%d",&t);
    while(t--){
        ans=0;
        scanf("%d",&n);
        for (i=1;i<=n;i++)
            scanf("%d",&a[i]);
        count(1,n);
        printf("%lld\n",ans);
    }
}