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# Longest Common Subsequence

Updated: Mar 25, 2021

Given two strings text1 and text2, return the length of their longest common subsequence.

A subsequence 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. (eg, "ace" is a subsequence of "abcde" while "aec" is not). A common subsequence of two strings is a subsequence that is common to both strings.

If there is no common subsequence, return 0.

Example 1:

```Input: text1 = "abcde", text2 = "ace"
Output: 3
Explanation: The longest common subsequence is "ace" and its length is 3.
```

Example 2:

```Input: text1 = "abc", text2 = "abc"
Output: 3
Explanation: The longest common subsequence is "abc" and its length is 3.
```

Example 3:

```Input: text1 = "abc", text2 = "def"
Output: 0
Explanation: There is no such common subsequence, so the result is 0.
```

Constraints:

• 1 <= text1.length <= 1000

• 1 <= text2.length <= 1000

• The input strings consist of lowercase English characters only.

Solution:

```class Solution {
public int longestCommonSubsequence(String text1, String text2) {

int[][] result = new int[text1.length()+1][text2.length()+1];

for(int i=1;i<=text1.length();i++)
{
for(int j=1;j<=text2.length();j++)
{
if(text1.charAt(i-1)==text2.charAt(j-1))
{
result[i][j] = result[i-1][j-1]+1;
}
else
{
result[i][j] = Math.max(result[i-1][j],result[i][j-1]);
}

}
}

return result[text1.length()][text2.length()];

}

}```