UVA 12504 Updating a Dictionary

#include<iostream>
#include<vector>
#include<string>
#include<type_traits>
#include<sstream>
#include<tuple>
#include<bitset>
#include<regex>
#include<set>
#include<stack>
#include<queue>
#include<map>
using namespace std;

int T;

void Explain(map<string,string>& str2str,string source){
	vector<int> index1, index2;
	for (int i = 0; i < source.size(); i++){
		if (source[i] == ':') index1.push_back(i);
		if (source[i] == ',') index2.push_back(i);
	}
	index2.push_back(-1);
	int pos1 = 0;
	for (int i = 0; i < index1.size(); i++){
		string key = source.substr(pos1,index1[i]-pos1);
		string value;
		if (index2[i] != -1){
			value = source.substr(index1[i] + 1, index2[i] - index1[i] - 1);
			pos1 = index2[i] + 1;
		}
		else{
			value = source.substr(index1[i]+1);
		}
		str2str[key] = value;
	}
}

int main(){
	cin >> T;
	string del;
	getline(cin,del);
	while (T--){
		string s1;
		string s2;
		getline(cin,s1);
		getline(cin,s2);
		s1 = s1.substr(1,s1.size()-2);
		s2 = s2.substr(1,s2.size()-2);
		map<string, string> ms1;
		map<string, string> ms2;
		Explain(ms1, s1);
		Explain(ms2,s2);
		vector<string> Add;
		vector<string> Remove;
		vector<string> Change;
		auto it1 = ms1.begin();
		auto it2 = ms2.begin();
		while (it1 != ms1.end() && it2 != ms2.end()){
			string key1 = it1->first;
			string value1 = it1->second;
			string key2 = it2->first;
			string value2 = it2->second;
			if (key1 == key2){
				if (value1 != value2){
					Change.push_back(key1);
				}
				it1++;
				it2++;
			}
			else{
				if (ms2.find(key1) == ms2.end()){
					Remove.push_back(key1);
					it1++;
				}
				if (ms1.find(key2) == ms1.end()){
					Add.push_back(key2);
					it2++;
				}
			}
		}
		while (it1 != ms1.end()){
			Remove.push_back(it1->first);
			it1++;
		}
		while (it2 != ms2.end()){
			Add.push_back(it2->first);
			it2++;
		}
		bool flag = false;
		if (Add.size()){
			cout << "+";
			flag = true;
			for (int i = 0; i < Add.size(); i++){
				cout << Add[i];
				if (i < Add.size() - 1) cout << ',';
			}
			cout << endl;
		}
		
		if (Remove.size()){
			flag = true;
			cout << "-";
			for (int i = 0; i < Remove.size(); i++){
				cout << Remove[i];
				if (i < Remove.size() - 1) cout << ",";
			}
			cout << endl;
		}
		
		if (Change.size()){
			flag = true;
			cout << "*";
			for (int i = 0; i < Change.size(); i++){
				cout << Change[i];
				if (i < Change.size() - 1) cout << ",";
			}
			cout << endl;
		}
		if (!flag){
			cout << "No changes" << endl;
		}
		cout << endl;
	}
	//system("pause");
	return 0;
}