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

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, text1: str, text2: str) -> int:
        dp = [[0 for j in range(len(text2) + 1)] for i in range(len(text1) + 1)]

        for i in range(len(text1) - 1, -1, -1):
            for j in range(len(text2) - 1, -1, -1):
                if text1[i] == text2[j]:
                    dp[i][j] = 1 + dp[i + 1][j + 1]
                else:
                    dp[i][j] = max(dp[i][j + 1], dp[i + 1][j])

        return dp[0][0]