<p>Given an integer <code>n</code>, your task is to count how many strings of length <code>n</code> can be formed under the following rules:</p>

<ul>
	<li>Each character is a lower case vowel&nbsp;(<code>&#39;a&#39;</code>, <code>&#39;e&#39;</code>, <code>&#39;i&#39;</code>, <code>&#39;o&#39;</code>, <code>&#39;u&#39;</code>)</li>
	<li>Each vowel&nbsp;<code>&#39;a&#39;</code> may only be followed by an <code>&#39;e&#39;</code>.</li>
	<li>Each vowel&nbsp;<code>&#39;e&#39;</code> may only be followed by an <code>&#39;a&#39;</code>&nbsp;or an <code>&#39;i&#39;</code>.</li>
	<li>Each vowel&nbsp;<code>&#39;i&#39;</code> <strong>may not</strong> be followed by another <code>&#39;i&#39;</code>.</li>
	<li>Each vowel&nbsp;<code>&#39;o&#39;</code> may only be followed by an <code>&#39;i&#39;</code> or a&nbsp;<code>&#39;u&#39;</code>.</li>
	<li>Each vowel&nbsp;<code>&#39;u&#39;</code> may only be followed by an <code>&#39;a&#39;</code>.</li>
</ul>

<p>Since the answer&nbsp;may be too large,&nbsp;return it modulo&nbsp;<code>10^9 + 7</code>.</p>

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

<pre>
<strong>Input:</strong> n = 1
<strong>Output:</strong> 5
<strong>Explanation:</strong> All possible strings are: &quot;a&quot;, &quot;e&quot;, &quot;i&quot; , &quot;o&quot; and &quot;u&quot;.
</pre>

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

<pre>
<strong>Input:</strong> n = 2
<strong>Output:</strong> 10
<strong>Explanation:</strong> All possible strings are: &quot;ae&quot;, &quot;ea&quot;, &quot;ei&quot;, &quot;ia&quot;, &quot;ie&quot;, &quot;io&quot;, &quot;iu&quot;, &quot;oi&quot;, &quot;ou&quot; and &quot;ua&quot;.
</pre>

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

<pre>
<strong>Input:</strong> n = 5
<strong>Output:</strong> 68</pre>

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

<ul>
	<li><code>1 &lt;= n &lt;= 2 * 10^4</code></li>
</ul>

class Solution {
public:
  //  char vowels[]={'a','e','i','o','u'};
    int mod=1e9+7;
    int func(int ind,int n,char prev,vector<vector<int>> &dp)
    {
        if(ind==n)
        {
            return 1;
        }

        int ways=0;
        if(dp[ind][prev-'a']!=-1)
        {
            return dp[ind][prev-'a'];
        }

        for(int i=0;i<5;i++)
        {
            if(i==0)
            {
                if(prev=='u' || prev=='i'|| prev=='e' || prev=='x')
                {
                    ways=(ways+func(ind+1,n,'a',dp))%mod;
                }
            }
            else if(i==1)
            {
                if(prev=='a' || prev=='i' || prev=='x')
                {
                    ways=(ways+func(ind+1,n,'e',dp))%mod;
                }
            }
            else if(i==2)
            {
                if(prev=='e' || prev=='o' || prev=='x')
                {
                    ways=(ways+func(ind+1,n,'i',dp))%mod;
                }
            }
            else if(i==3)
            {
                if(prev=='i' || prev=='x')
                {
                    ways=(ways+func(ind+1,n,'o',dp))%mod;
                }
            }
            else{
                if(prev=='i' || prev=='o' || prev=='x')
                {
                    ways=(ways+func(ind+1,n,'u',dp))%mod;
                }
            }
        }

        return dp[ind][prev-'a']=ways;

        
    }

    int countVowelPermutation(int n) {

        vector<vector<int>> dp(n,vector<int>(26,-1));

        return func(0,n,'x',dp)%mod;

    }
};
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