hdu-2838（Cow Sorting）----》树状数组

#include
#include

typedef __int64 LL;
const LL M = 100005;

LL a[M],c[M];
LL n;

LL lowbit(LL x)
{
    return x&(-x);
}
void add(LL pos,LL x)
{
    LL num = pos;
    while(pos <= n)
    {
        a[pos] += num;
        c[pos] += x;
        pos += lowbit(pos);
    }
}
LL get_sum1(LL pos)
{
    LL res = 0;
    while(pos > 0)
    {
        res += c[pos];
        pos -= lowbit(pos);
    }
    return res;
}
LL get_sum2(LL pos)
{
    LL res = 0;
    while(pos > 0)
    {
        res += a[pos];
        pos -= lowbit(pos);
    }
    return res;
}
int main()
{
    LL m,x,ret,k;
    while(~scanf("%I64d",&n))
    {
        LL ret = 0;
        memset(a,0,sizeof(a));
        memset(c,0,sizeof(c));
        for(LL i = 1;i <= n;i++)
        {
            scanf("%I64d",&m);
            add(m,1);
            x = i - get_sum1(m);
            if(x)
            {
                 k = get_sum2(n) - get_sum2(m);
                 ret += x * m + k;
            }
        }
        printf("%I64d\n",ret);
    }
}