LeetCode Buddy Strings

LeetCode

Given two strings 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].

For example, swapping at indices 0 and 2 in "abcd" results in "cbad".

Example 1:

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.

Example 2:

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.

Example 3:

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.

Constraints: 1 <= s.length, goal.length <= 2 * 10<sup>4</sup>
* s and goal consist of lowercase letters.

题目大意：

给定两字符串，交换一次使得他们相等

解题思路：

三种情况：长度不等，完全相等（若至少有一个重复，即满足题意），两次不同

解题步骤：

N/A

注意事项：

三种情况：长度不等，完全相等，两次不同

Python代码：

def buddyStrings(self, s: str, goal: str) -> bool:
	if len(s) != len(goal):
		return False
	if s == goal and len(set(s)) < len(goal): # any dups
		return True
	diff = [(a, b) for a, b in zip(s, goal) if a != b]
	return True if len(diff) == 2 and diff[0] == diff[1][::-1] else False

算法分析：

时间复杂度为O(n)，空间复杂度O(1)