题解：UVA12538 自带版本控制功能的IDE Version Controlled IDE

#include<bits/stdc++.h>
#include<ext/rope>
using namespace std;
using namespace __gnu_cxx;
int Q,id,opt,p,v,c,cnt;
rope<char> str[50005],lst,tmp;
string s;
int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin >> Q;
	while(Q --){
		cin >> opt;
		if(opt == 1){
			cin >> p >> s;
			p -= cnt;
			lst.insert(p,s.c_str());
			str[++id] = lst;
		}else if(opt == 2){
			cin >> p >> c;
			p -= cnt,c -= cnt;
			lst.erase(p - 1,c);
			str[++id] = lst;
		}else{
			cin >> v >> p >> c;
			v -= cnt,p -= cnt,c -= cnt;
			tmp.clear();
			tmp = str[v].substr(p - 1,c);
			cnt += count(tmp.begin(),tmp.end(),'c');
			cout << tmp << '\n';
		}
	}
	return 0;
}