<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 check_ch(string p,int j){
        while(j < p.size()){
            if(p[j] == '*'){
                j++;
                continue;
            }
            if((p[j] >= 97 && p[j] <= 122) || (p[j] == '.')){
                if(j+1 < p.size() &&(p[j+1] == '*')){
                j++;
                continue;
                }
                else{
                    return false;
                }
            }
        }
        return true;
    }
    vector<vector<int>>dp;
    bool solve(int i, int j,string &s,string &p ,int n,int m){
        //base cases
        if(j >= m && i < n)return false;
        if(j >=m && i >= n)return true;
        if(i >= n && j < m) return check_ch(p,j);
        //cases
        if(dp[i][j] != -1){
            return dp[i][j];
        }
        //1.st
        bool ans = false;
        if(j+1 < m && p[j+1] == '*'){
            ans |= solve(i,j+2,s,p,n,m);
            if((s[i] == p[j] || p[j] == '.')){
                ans |= solve(i+1,j,s,p,n,m);
            }
        }
        if(s[i] == p[j] || p[j] == '.'){
            ans |=  solve(i+1,j+1,s,p,n,m);
        }
        else{
            ans |= false;
        }
        dp[i][j] = ans;
        //cout<<i<<" "<<j<<" "<<dp[i][j]<<endl;
        return dp[i][j];

    }
    bool isMatch(string s, string p) {
        int n = s.size();
        int m = p.size();
        dp.resize(n,vector<int>(m,-1));
        return solve(0,0,s,p,n,m);
    }
};
12556