<p>Given a string containing digits from <code>2-9</code> inclusive, return all possible letter combinations that the number could represent. Return the answer in <strong>any order</strong>.</p>

<p>A mapping of digits to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.</p>
<img alt="" src="https://assets.leetcode.com/uploads/2022/03/15/1200px-telephone-keypad2svg.png" style="width: 300px; height: 243px;" />
<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> digits = &quot;23&quot;
<strong>Output:</strong> [&quot;ad&quot;,&quot;ae&quot;,&quot;af&quot;,&quot;bd&quot;,&quot;be&quot;,&quot;bf&quot;,&quot;cd&quot;,&quot;ce&quot;,&quot;cf&quot;]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> digits = &quot;&quot;
<strong>Output:</strong> []
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> digits = &quot;2&quot;
<strong>Output:</strong> [&quot;a&quot;,&quot;b&quot;,&quot;c&quot;]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>0 &lt;= digits.length &lt;= 4</code></li>
	<li><code>digits[i]</code> is a digit in the range <code>[&#39;2&#39;, &#39;9&#39;]</code>.</li>
</ul>

class Solution {
public:
    void printVector(vector<string> res)
    {
        for(string str :res)
        {
            std::cout<<str<<std::endl;
        }
        std::cout<<"----------------------------------------------"<<std::endl;
    }
    vector<string> dfsPattern(std::unordered_map<char, vector<char>>& hmap, string digit, int index, string partial) 
    {
        vector<string> result;
        if (index >= digit.size()) {
            result.push_back(partial);
           // printVector(result);
            return result;
        }

        vector<char> curr_vec = hmap[digit[index]];

        for (char c : curr_vec) {
            vector<string> temp_result = dfsPattern(hmap, digit, index + 1, partial + c);
            result.insert(result.end(), temp_result.begin(), temp_result.end());
            printVector(temp_result);
        }
        return result;
    }

    vector<string> letterCombinations(string digits) {
        std::unordered_map<char, vector<char>> hmap;

        hmap['2'] = {'a', 'b', 'c'};
        hmap['3'] = {'d', 'e', 'f'};
        hmap['4'] = {'g', 'h', 'i'}; // Corrected to 'g', 'h', 'i'
        hmap['5'] = {'j', 'k', 'l'}; // Added missing digit '5'
        hmap['6'] = {'m', 'n', 'o'};
        hmap['7'] = {'p', 'q', 'r', 's'};
        hmap['8'] = {'t', 'u', 'v'};
        hmap['9'] = {'w', 'x', 'y', 'z'};

        if (digits.empty()) return {};

        return dfsPattern(hmap, digits, 0, "");
    }
};
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