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Tested Python solution for LeetCode 859 with 22 pytest cases. Generate a practice environment with lcpy.
lcpy gen -n 859 # by problem number
lcpy gen -s buddy_strings # by problem name
s and goal, return true if you can swap two letters in s so the result is equal to goal, otherwise, return false.
Swapping letters is defined as taking two indices i and j (0-indexed) such that i != j and swapping the characters at s[i] and s[j].
0 and 2 in "abcd" results in "cbad".Input: s = "ab", goal = "ba"
Output: true
Explanation: You can swap s[0] = 'a' and s[1] = 'b' to get "ba", which is equal to goal.
Input: s = "ab", goal = "ab"
Output: false
Explanation: The only letters you can swap are s[0] = 'a' and s[1] = 'b', which results in "ba" != goal.
Input: s = "aa", goal = "aa"
Output: true
Explanation: You can swap s[0] = 'a' and s[1] = 'a' to get "aa", which is equal to goal.
class Solution:
# Time: O(n)
# Space: O(1)
def buddy_strings(self, s: str, goal: str) -> bool:
if len(s) != len(goal):
return False
if s == goal:
return len(set(s)) < len(s)
diffs = [i for i, (a, b) in enumerate(zip(s, goal, strict=True)) if a != b]
if len(diffs) != 2:
return False
i, j = diffs
return s[i] == goal[j] and s[j] == goal[i]
| Time | Space |
|---|---|
| O(n) | O(1) |