[Solved] Given two strings text1 and text2, return the length of their longest common subsequence. If there is no common subsequence, return 0.

Question

Given two strings text1 and text2, return the length of their longest common subsequenceIf there is no common subsequence, return 0.

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.

  • For example, "ace" is a subsequence of "abcde".

common subsequence of two strings is a subsequence that is common to both strings.

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, text2.length <= 1000
  • text1 and text2 consist of only lowercase English characters.

Python Solution

class Solution:
    def longestCommonSubsequence(self, text1: str, text2: str) -> int:
        a = len(text1)
        b = len(text2)
        
        matrix = [[0 for _ in range(b+1)] for _ in range(a+1)]
        
        for i in range(1,a+1):
            for j in range(1,b+1):
                if text1[i-1]==text2[j-1]:
                    matrix[i][j] = matrix[i-1][j-1]+1
                else:
                    matrix[i][j] = max(matrix[i-1][j],matrix[i][j-1])
        
        return matrix[-1][-1]
Abhishek Sharma
Abhishek Sharma

Started my Data Science journey in my 2nd year of college and since then continuously into it because of the magical powers of ML and continuously doing projects in almost every domain of AI like ML, DL, CV, NLP.

Articles: 520

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