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Tested Python solution for LeetCode 564 with 27 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 564 # by problem number
lcpy gen -s find_the_closest_palindrome # by problem name
n representing an integer, return the closest integer (not including itself), which is a palindrome. If there is a tie, return the smaller one.
The closest is defined as the absolute difference minimized between two integers.
Input: n = "123"
Output: "121"
Input: n = "1"
Output: "0"
1 <= n.length <= 18n consists of only digits.n does not have leading zeros.n is representing an integer in the range [1, 10^18 - 1].class Solution:
# Time: O(len(n))
# Space: O(len(n))
def nearest_palindromic(self, n: str) -> str:
num = int(n)
length = len(n)
candidates: set[int] = {10 ** (length - 1) - 1, 10**length + 1}
prefix = int(n[: (length + 1) // 2])
for p in (prefix - 1, prefix, prefix + 1):
left = str(p)
mirrored = left if length % 2 == 0 else left[:-1]
candidates.add(int(left + mirrored[::-1]))
candidates.discard(num)
best: int = candidates.pop()
for cand in candidates:
if (abs(cand - num), cand) < (abs(best - num), best):
best = cand
return str(best)
| Time | Space |
|---|---|
| O(len(n)) | O(len(n)) |