leetcode-1790-easy

Check if One String Swap Can Make Strings Equal

You are given two strings s1 and s2 of equal length. A string swap is an operation where you choose two indices in a string (not necessarily different) and swap the characters at these indices.

Return true if it is possible to make both strings equal by performing at most one string swap on exactly one of the strings. Otherwise, return false.

 

Example 1:

Input: s1 = "bank", s2 = "kanb"
Output: true
Explanation: For example, swap the first character with the last character of s2 to make "bank".
Example 2:

Input: s1 = "attack", s2 = "defend"
Output: false
Explanation: It is impossible to make them equal with one string swap.
Example 3:

Input: s1 = "kelb", s2 = "kelb"
Output: true
Explanation: The two strings are already equal, so no string swap operation is required.
 

Constraints:

1 <= s1.length, s2.length <= 100
s1.length == s2.length
s1 and s2 consist of only lowercase English letters.

思路一： 遍历字符串，记录字符不同的位置，完全分类，有以下几种分类

• 没有不同的位置 true
• 有一个不同的位置 false
• 有两个不同的位置 ?
• 有三个以上不同的位置 false

只需要对第三种情况进行字符判断即可，其他三种情况可以直接给出 bool 值

public boolean areAlmostEqual(String s1, String s2) {
	int idx1 = -1;
	int idx2 = -1;
	for (int i = 0; i < s1.length(); i++) {
		if (s1.charAt(i) != s2.charAt(i)) {
			if (idx1 == -1) idx1 = i;
			else if (idx2 == -1) idx2 = i;
			else return false;
		}
	}

	if (idx1 == -1 && idx2 == -1) return true;
	if (idx1 != -1 && idx2 != -1) return (s1.charAt(idx1) == s2.charAt(idx2) && s1.charAt(idx2) == s2.charAt(idx1));
	return  false;
}