LeetCode/1143_Longest_Common_Subsequence.py at main · AnmolPatel20/LeetCode · GitHub

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"""
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.

"""


class Solution:
    def longestCommonSubsequence(self, text1: str, text2: str) -> int:
        n, m = len(text1), len(text2)

        #DP Table
        dp = [[0]* (m+1) for _ in range(n+1)]

        #Fill the Table
        for i in range(1, n+1):
            for j in range(1, m+1):
                if text1[i-1] == text2[j-1]:
                    dp[i][j] = 1 + dp[i-1][j-1]
                else:
                    dp[i][j] = max(dp[i-1][j] , dp[i][j-1])

        return dp[n][m]