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.
Input: text1 = "abcde", text2 = "ace" Output: 3 Explanation: The longest common subsequence is "ace" and its length is 3.
Input: text1 = "abc", text2 = "abc" Output: 3 Explanation: The longest common subsequence is "abc" and its length is 3.
Input: text1 = "abc", text2 = "def" Output: 0 Explanation: There is no such common subsequence, so the result is 0.
- 1 <= text1.length, text2.length <= 1000
- text1 and text2 consist of only lowercase English characters.
I solved this problem like this.
If we use dp, we can solve this problem.
class Solution: def longestCommonSubsequence(self, text1: str, text2: str) -> int: t1, t2 = len(text1), len(text2) dp = [[0 for x in range(t2)] for _ in range(t1)] for r in range(t1): for c in range(t2): left = dp[r][c-1] if c > 0 else 0 up = dp[r-1][c] if r > 0 else 0 left_up = dp[r-1][c-1] if c > 0 and r > 0 else 0 if text1[r] == text2[c]: dp[r][c] = left_up + 1 else: dp[r][c] = max(left, up) return dp[-1][-1]