<p>Given two strings <code>text1</code> and <code>text2</code>, return <em>the length of their longest <strong>common subsequence</strong>. </em>If there is no <strong>common subsequence</strong>, return <code>0</code>.</p>

<p>A <strong>subsequence</strong> of a string is a new string generated from the original string with some characters (can be none) deleted without changing the relative order of the remaining characters.</p>

<ul>
	<li>For example, <code>&quot;ace&quot;</code> is a subsequence of <code>&quot;abcde&quot;</code>.</li>
</ul>

<p>A <strong>common subsequence</strong> of two strings is a subsequence that is common to both strings.</p>

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

<pre>
<strong>Input:</strong> text1 = &quot;abcde&quot;, text2 = &quot;ace&quot; 
<strong>Output:</strong> 3  
<strong>Explanation:</strong> The longest common subsequence is &quot;ace&quot; and its length is 3.
</pre>

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

<pre>
<strong>Input:</strong> text1 = &quot;abc&quot;, text2 = &quot;abc&quot;
<strong>Output:</strong> 3
<strong>Explanation:</strong> The longest common subsequence is &quot;abc&quot; and its length is 3.
</pre>

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

<pre>
<strong>Input:</strong> text1 = &quot;abc&quot;, text2 = &quot;def&quot;
<strong>Output:</strong> 0
<strong>Explanation:</strong> There is no such common subsequence, so the result is 0.
</pre>

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

<ul>
	<li><code>1 &lt;= text1.length, text2.length &lt;= 1000</code></li>
	<li><code>text1</code> and <code>text2</code> consist of only lowercase English characters.</li>
</ul>

class Solution {
public:
    int maxCommon(int ind1, int ind2, string& str1, string& str2, vector<vector<int>>& dp){
        if(ind1 < 0 || ind2 < 0)
            return 0;

        if(dp[ind1][ind2] != -1)
            return dp[ind1][ind2];

        if(str1[ind1] == str2[ind2])
            return dp[ind1][ind2] = 1 + maxCommon(ind1-1, ind2-1, str1, str2, dp);
        
        int pickL = maxCommon(ind1-1, ind2, str1, str2, dp);
        int pickR = maxCommon(ind1, ind2-1, str1, str2, dp);
        return dp[ind1][ind2] = max(pickL, pickR);
    }
    int longestCommonSubsequence(string text1, string text2) {
        if(text1 == text2)
            return text1.length();

        int l1 = text1.size(), l2 = text2.size();
        vector<vector<int>> dp(l1, vector<int>(l2, -1));

        return maxCommon(l1-1, l2-1, text1, text2, dp);
    }   
};
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