Tree: Huffman decoding challenge on hackerrank.com

[hackerrank]Tree_huffman_decoding.cpp

#include <stack>

string get_sequence(vector<int> source) 
{
    string ret;
    for (int i = 0; i < source.size(); i++) 
    {
        ret.push_back(to_string(source[i])[0]);
    }
    
    return ret;
}

map<string, char> build_sequence_map(node* root) 
{
    node* curNode = root;

    stack<node*> nodes;
    nodes.push(curNode);
    
    vector<int> curPath;
    unordered_set<node*> metNodes;
    map<string, char> sequences;
    
    while (!nodes.empty()) 
    {

        if (curNode->data != '\0' && metNodes.find(curNode) == metNodes.end()) 
        {
            string seq = get_sequence(curPath);
            sequences.emplace(seq, curNode->data);
            
            curPath.erase(curPath.end() - 1);
           
            node* previous = nodes.top();
            nodes.pop();
            
            metNodes.insert(curNode);
            curNode = previous;
            continue;
        }
        
        if (metNodes.find(curNode) == metNodes.end())
            metNodes.insert(curNode);
        
        
        if (curNode->left != nullptr && metNodes.find(curNode->left) == metNodes.end()) 
        {
            nodes.push(curNode);
            curNode = curNode->left;
            curPath.push_back(0);
        } 
        else if(curNode->right != nullptr && metNodes.find(curNode->right) == metNodes.end())
        {
            nodes.push(curNode);
            curNode = curNode->right;
            curPath.push_back(1);
        }
        else
        {
            curPath.erase(curPath.end() - 1);
            
            node* previous = nodes.top();
            nodes.pop();
            
            curNode = previous;
        }
    }
    
    return sequences;
}

void decode_huff(node* root, string s) 
{
    map<string, char> sequences = build_sequence_map(root);
    
    string output;
    string cur;
    for (int i = 0; i < s.size(); i++) {
        cur += s[i];
        
        if (sequences.find(cur) != sequences.end()) {
            output += sequences[cur];
            cur.clear();
        }
    }
    
    cout << output << endl;
}