Play this article

### Problem

Given two strings text1 and text2, return the length of their longest common subsequence. If there is no common subsequence, return 0. This is similar to the Leetcode Problem - Longest Common Subsequence

### Approach

The approach would be based on dynamic programming. We take a 2d array with rows and columns indicating string 1 and string 2 respectively. Then we use the below code to calculate the common subsequence of the previous diagonal element if equal else we take the max of the upper and left element.

```
class Solution {
public int longestCommonSubsequence(String text1, String text2) {
int m = text1.length(), n = text2.length();
int[][] dp = new int[m + 1][n + 1];
for(int i = 1; i <= m; i++)
for(int j = 1; j <= n; j++)
if(text1.charAt(i-1) == text2.charAt(j-1)) dp[i][j] = dp[i-1][j-1] + 1;
else dp[i][j] = Math.max(dp[i - 1][j], dp[i][j - 1]);
return dp[m][n];
}
}
```

Do have a look at the discuss section for more optimized solutions if available - LeetCode Discuss