decoderecursive.cpp

#include <bits/stdc++.h>
using namespace std;

string nstr;
string decode(string str, int *i)
{
	string retval;
	while (*i < str.length() && str[*i] != ']')
	{
		if (!isdigit(str[*i]))
		{
			if (str[*i] == '[')
			{
				int n = stoi(nstr);
				nstr = "";
				*i += 1;
				string istr = decode(str, i);
				*i += 1;
				while (n-- > 0)
				{
					retval += istr;
				}
			}
			else
				retval += str[(*i)++];
		}
		else
		{
			nstr += str[(*i)++];
		}
	}
	return retval;
}

int main()
{
	string str;
	cout << "Enter the string to be decoded : ";
	cin >> str;
	int i = 0;
	string ans = decode(str, &i);
	cout << ans;
}