<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:
int n;
vector<string>result;
void find(int idx,string &temp,string &digits,unordered_map<char,string>&mp){
    if(idx>=n){
        result.push_back(temp);
        return;
    }
    char ch=digits[idx];
    string str=mp[ch];
    for(int i=0;i<str.length();i++){
        temp.push_back(str[i]);
        find(idx+1,temp,digits,mp);
        temp.pop_back();

    }
}
    vector<string> letterCombinations(string digits) {
        n=digits.size();
        if(n==0){
            return{};
        }
        unordered_map<char,string>mp;
        mp['2']="abc";
        mp['3']="def";
        mp['4']="ghi";
        mp['5']="jkl";
        mp['6']="mno";
        mp['7']="pqrs";
        mp['8']="tuv";
        mp['9']="wxyz";
        string temp="";
        find(0,temp,digits,mp);
        return result;

        
    }
};
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