Decode String - Stacks GFG

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

string decode(string str)
{
    stack<int> integerstack;
    stack<char> stringstack;
    string temp = "", result = "";
    for (int i = 0; i < str.length(); i++)
    {
        int count = 0;

        if (str[i] >= '0' && str[i] <='9')
        {
            while (str[i] >= '0' && str[i] <= '9')
            {
                count = count * 10 + str[i] - '0';
                i++;
            }

            i--;
            integerstack.push(count);
        }
        else if (str[i] == ']')
        {
            temp = "";
            count = 0;

            if (! integerstack.empty())
            {
                count = integerstack.top();
                integerstack.pop();
            }

            while (! stringstack.empty() && stringstack.top()!='[' )
            {
                temp = stringstack.top() + temp;
                stringstack.pop();
            }

            if (! stringstack.empty() && stringstack.top() == '[')
                stringstack.pop();

            for (int j = 0; j < count; j++)
                result = result + temp;

            for (int j = 0; j < result.length(); j++)
                stringstack.push(result[j]);

            result = "";
        }

        else if (str[i] == '[')
        {
            if (str[i-1] >= '0' && str[i-1] <= '9')
                stringstack.push(str[i]);

            else
            {
                stringstack.push(str[i]);
                integerstack.push(1);
            }
        }

        else
            stringstack.push(str[i]);
    }

    while (! stringstack.empty())
    {
        result = stringstack.top() + result;
        stringstack.pop();
    }

    return result;
}
int main()
{
    int t;
    
    cin >> t;
    while(t--) {
        string str;
        cin >> str;
        cout << decode(str) << endl;
    }
    return 0;
}