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Tested Python solution for LeetCode 205 with 18 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 205 # by problem number
lcpy gen -s isomorphic_strings # by problem name
s and t, determine if they are isomorphic.
Two strings s and t are isomorphic if the characters in s can be replaced to get t.
All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character, but a character may map to itself.
Input: s = "egg", t = "add"
Output: true
Explanation: The strings s and t can be made identical by:
- Mapping 'e' to 'a'.
- Mapping 'g' to 'd'.
Input: s = "f11", t = "b23"
Output: false
Explanation: The strings s and t can not be made identical as '1' needs to be mapped to both '2' and '3'.
Input: s = "paper", t = "title"
Output: true
class Solution:
# Time: O(n)
# Space: O(k) where k is the alphabet size
def is_isomorphic(self, s: str, t: str) -> bool:
s_to_t: dict[str, str] = {}
t_to_s: dict[str, str] = {}
for cs, ct in zip(s, t, strict=True):
if cs in s_to_t and s_to_t[cs] != ct:
return False
if ct in t_to_s and t_to_s[ct] != cs:
return False
s_to_t[cs] = ct
t_to_s[ct] = cs
return True
| Time | Space |
|---|---|
| O(n) | O(k) where k is the alphabet size |