Educational Codeforces Round 93 (Rated for Div. 2) C. Good Subarrays

题目链接
思路：
将每一位上的数组-1，将问题转化为求区间和为0的问题，再维护一个前缀和即可。
代码：

#include
#define int long long
#define IOS ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
const int N=210;
const int M=2e4+5;
const double eps=1e-8;
const int mod=998244353;
const int inf=0x7fffffff;
const double pi=3.1415926;
using namespace std;
signed main()
{
    IOS;
    int t;
	cin>>t;
	while (t--)
	{
		int n;
		cin>>n;
		string s;
		map<int,int>mp;
		cin>>s;
		int sum=0,ans=0;
		mp.clear();
		for (int i=0;i<n;i++)
		{
			sum+=s[i]-'0'-1;
			if(sum==0)
                ans++;
			ans+=mp[sum];
			mp[sum]++;
		}
		cout<<ans<<endl;
	}
	return 0;
}