nyist 117 求逆序數（哈希表+樹狀數組）

題目鏈接：http://acm.nyist.edu.cn/JudgeOnline/problem.php?pid=117

題意：漢語題。。。

哈希表不說了，樹狀數組插點問線。

#include<iostream>
#include<cstring>
#include<cstdio>
#include<ctime>
#include<algorithm>
using namespace std;

#define clr(arr,v) memset(arr,v,sizeof(arr))

const int M = 10000007;
template<class T,int size>
class Hash{
public:
	Hash(){}
	void clear(){
		pos = index = 0;
		clr(head,-1);
	}
	T& operator[](T value){
		return val[add(value)];
	}
	T add(T value){
		int v = value / M;
		for(int i = head[value%M];i != -1;i = next[i])
		{
			if(num[i] == v)
				return i;
		}
		num[pos] = v;
		val[pos] = ++index;
		next[pos] = head[value%M];
		head[value%M] = pos++;
		return pos-1;
	}
private:
	int index,pos,val[size],next[size],head[M];
	T num[size];
};

Hash<int,1000005> h;

int tree[1000005],num[1000005],num1[1000005];

int lowbit(int x) {return x&(-x);}

void update(int x)
{
	if(x <= 0) return ;
	tree[x] += 1;
	update(x - lowbit(x));
}

int get_num(int x,int n)
{
	if(x >= n) return tree[n];
	return tree[x]+get_num(x+lowbit(x),n);
}

int main()
{
	//freopen("1.txt","r",stdin);
	int T;
	scanf("%d",&T);
	while(T--)
	{
		h.clear();
		memset(tree,0,sizeof(tree));
		int n,val,t;
		long long sum = 0;
		scanf("%d",&n);
		for(int i = 0;i < n;++i)
		{
			scanf("%d",&num[i]);
			num1[i] = num[i];
		}
		sort(num1,num1+n);
		for(int i = 0;i < n;++i)
			h[ num1[i] ];
		for(int i = 0;i < n;++i)
		{
			t = h[ num[i] ];
			sum += get_num(t,n);
			update(t-1);
		}
		printf("%lld\n",sum);
	}
	//printf("%.2lf\n",(double)clock()/CLOCKS_PER_SEC);
	return 0;
}