rt，思路比较简洁，有可能是思路错了，代码如下

#include<bits/stdc++.h>

using namespace std;

int n, cnt;
map<int, int> mk;
map<pair<int, int>, int> mb;

int main()
{
	cin >> n;
	for(int i = 1; i <= n; i++)
	{
		int x, y, z;
		cin >> x >> y >> z;
		if(x == 1)
		{
			cnt++;
			mk[y]++;
			mb[make_pair(y, z)]++;
		}
		if(x == 2)
		{
			cout << cnt - mk[y] << endl;
		}
		if(x == 3)
		{
			int ovl = mb[make_pair(y, z)];
			//cout << ovl << endl;
			mb[make_pair(y, z)] -= ovl;
			mk[y] -= ovl;
			cnt -= ovl;
		}
	}
	return 0;
}