<p>Given an input string <code>s</code>&nbsp;and a pattern <code>p</code>, implement regular expression matching with support for <code>&#39;.&#39;</code> and <code>&#39;*&#39;</code> where:</p>

<ul>
	<li><code>&#39;.&#39;</code> Matches any single character.​​​​</li>
	<li><code>&#39;*&#39;</code> Matches zero or more of the preceding element.</li>
</ul>

<p>The matching should cover the <strong>entire</strong> input string (not partial).</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;aa&quot;, p = &quot;a&quot;
<strong>Output:</strong> false
<strong>Explanation:</strong> &quot;a&quot; does not match the entire string &quot;aa&quot;.
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;aa&quot;, p = &quot;a*&quot;
<strong>Output:</strong> true
<strong>Explanation:</strong> &#39;*&#39; means zero or more of the preceding element, &#39;a&#39;. Therefore, by repeating &#39;a&#39; once, it becomes &quot;aa&quot;.
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;ab&quot;, p = &quot;.*&quot;
<strong>Output:</strong> true
<strong>Explanation:</strong> &quot;.*&quot; means &quot;zero or more (*) of any character (.)&quot;.
</pre>

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

<ul>
	<li><code>1 &lt;= s.length&nbsp;&lt;= 20</code></li>
	<li><code>1 &lt;= p.length&nbsp;&lt;= 20</code></li>
	<li><code>s</code> contains only lowercase English letters.</li>
	<li><code>p</code> contains only lowercase English letters, <code>&#39;.&#39;</code>, and&nbsp;<code>&#39;*&#39;</code>.</li>
	<li>It is guaranteed for each appearance of the character <code>&#39;*&#39;</code>, there will be a previous valid character to match.</li>
</ul>

class Solution {
public:

    bool solve(string s, string p){
        cout<<s<<" "<<p<<endl;
        if(s==p)return true;
        if(p=="")return false;
        if(s!="" && (s[s.size() - 1] == p[p.size() - 1] || p[p.size() - 1] == '.')){
            cout<<"ok"<<endl;
            return solve(s.substr(0,s.size()-1) , p.substr(0,p.size()-1));
        }
        if(p[p.size() - 1] == '*'){
            int i = p.size()-1;
            while(p[i] == '*')i--;
            char c = p[i];
            cout<<c<<endl;
            if(c == '.'){
                int j = s.size() - 1;
                while(j>=0){
                    bool temp = solve(s.substr(0 , j+1) , p.substr(0,i));
                    j--;
                    if(temp == true)return true;
                }
                return solve(s.substr(0 , j+1) , p.substr(0,i));
            }else{
                int j=s.size() - 1;
                while(j>=0 && s[j] == c){
                    bool temp = solve(s.substr(0 , j+1) , p.substr(0,i));
                    j--;
                    if(temp == true)return true;
                }
                return solve(s.substr(0 , j+1) , p.substr(0,i));
            }
        }
        return false;
    }
    

    bool isMatch(string s, string p) {
        return solve(s,p);
    }
};
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