# 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()];
}
}
```