Leetcode 1143. Longest Common Subsequence. Python [Blind 75 Finally Done!]

1143. Longest Common Subsequence 

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

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.

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

A 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.

Solution :

class Solution:
    def longestCommonSubsequence(self, t1: str, t2: str) -> int:
        matrix = [[0 for j in range(len(t2)+1)] for i in range(len(t1)+1)]
        
        for i in range(len(t1)-1, -1, -1):
            for j in range(len(t2)-1, -1, -1):
                
                if t1[i]==t2[j]:
                    matrix[i][j] = 1 + matrix[i+1][j+1]
                else:
                    matrix[i][j] = max(matrix[i][j+1],matrix[i+1][j])
                    
        return matrix[0][0]
        

Explanation :