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Tested Python solution for LeetCode 516 with 16 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 516 # by problem number
lcpy gen -s longest_palindromic_subsequence # by problem name
s, find the longest palindromic subsequence’s length in s.
A subsequence is a sequence that can be derived from another sequence by deleting some or no elements without changing the order of the remaining elements.
Input: s = "bbbab"
Output: 4
Explanation: One possible longest palindromic subsequence is "bbbb".
Input: s = "cbbd"
Output: 2
Explanation: One possible longest palindromic subsequence is "bb".
1 <= s.length <= 1000s consists only of lowercase English letters.class Solution:
# Time: O(n^2)
# Space: O(n^2)
def longest_palindrome_subseq(self, s: str) -> int:
n = len(s)
dp = [[0] * n for _ in range(n)]
for i in range(n - 1, -1, -1):
dp[i][i] = 1
for j in range(i + 1, n):
if s[i] == s[j]:
dp[i][j] = dp[i + 1][j - 1] + 2
else:
dp[i][j] = max(dp[i + 1][j], dp[i][j - 1])
return dp[0][n - 1]
| Time | Space |
|---|---|
| O(n^2) | O(n^2) |