<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>

#include <vector>
#include <string>
#include <iostream>
#include <unordered_map>
#include <queue>
using namespace std;
class Solution {
 public:
  bool isMatch(string s, string p) {
    if(s.size()==0&&p.size()==0)return true;
    if(s.size()==0||p.size()==0)return false;
    s='.'+s;
    p='.'+p;
   vector<vector<bool>> dp;
   vector<bool> r;
   r.push_back(true);
   for(int i = 1;i<s.size();i++){
    r.push_back(false);
   }
   dp.push_back(r);
   for(int j = 1;j<p.size();j++){
    if(p[j]=='*'){
        r[0]=dp[dp.size()-1][0]||dp[dp.size()-2][0];
    }else r[0]=false;
    dp.push_back(r);
   }
   //i for p, j for s
   //p[0:i] s[0:j]匹配结果记录在dp
   for(int i = 1;i<p.size();i++){
    for(int j = 1;j<s.size();j++){
        if(p[i]==s[j]||p[i]=='.'){
            dp[i][j]=dp[i-1][j-1];
        }
        if(p[i]=='*'){
            if(p[i-1]==s[j]||p[i-1]=='.'){
                dp[i][j]=dp[i-2][j]||dp[i][j-1]||dp[i-1][j];
            }else {
                dp[i][j]=dp[i-2][j];
            }
        }
    }
   }
   return dp[p.size()-1][s.size()-1];
  }
};
10493