Leetcode 1143. Longest Common Subsequence

Seawolf

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.

class Solution:
    def longestCommonSubsequence(self, text1: str, text2: str) -> int:
        m = len(text1)
        n = len(text2)
        dp = [[0 for _ in range(n + 1)] for _ in range(m + 1)]
        
        for i in range(1, m + 1):
            for j in range(1, n + 1):
                if text1[i - 1] != text2[j - 1]:
                    dp[i][j] = max(dp[i - 1][j], dp[i][j - 1])
                else:
                    dp[i][j] = dp[i - 1][j - 1] + 1
        return dp[m][n]