Codeforces Round #721 (Div. 2) C. Sequence Pair Weight

Posted 2021-05-24 尘封陌路

如图：

AC代码：

	#include<bits/stdc++.h>
	using namespace std;
	const int N=1e5+10;
	typedef long long ll;
	ll a[N];
	map<ll,ll> mp;
	
	int main()
	{
		int t;
		cin>>t;
		while(t--)
		{
			int n;
			cin>>n;
			mp.clear();
			ll ans=0;
			for(int i=1;i<=n;i++)
			{
				cin>>a[i];
				ans+=mp[a[i]]*(n-i+1);
				mp[a[i]]+=i;
			}
			cout<<ans<<"\\n";
		}
		return 0;
	}