Java
/**
Given two strings A and B of lowercase letters, return true if and only if we can swap two letters in A
so that the result equals B.
Example 1:
Input: A = "ab", B = "ba"
Output: true
Example 2:
Input: A = "ab", B = "ab"
Output: false
Example 3:
Input: A = "aa", B = "aa"
Output: true
Example 4:
Input: A = "aaaaaaabc", B = "aaaaaaacb"
Output: true
Example 5:
Input: A = "", B = "aa"
Output: false
Note:
0 <= A.length <= 20000
0 <= B.length <= 20000
A and B consist only of lowercase letters.
*/
public class Buddy_Strings {
class Solution {
public boolean buddyStrings(String A, String B) {
if (A == null || B == null) {
return false;
}
if (A.length() != B.length()) {
return false;
}
if (A.equals(B)) {
int[] count = new int[26];
for (int i = 0; i < A.length(); ++i)
count[A.charAt(i) - 'a']++;
for (int c: count) {
if (c > 1) {
return true;
}
}
return false;
}
// abcd, badc => false
int p1 = -1;
int p2 = -1;
for (int i = 0; i < A.length(); i++) {
if (A.charAt(i) != B.charAt(i)) {
// record this position
if (p1 < 0) {
p1 = i;
} else if (p2 < 0) {
p2 = i;
} else {
return false; // found the 2 positions, for abcd and badc, also need to check the rest strings
}
}
}
if (p1 < 0 | p2 < 0) {
return false;
}
return A.charAt(p1) == B.charAt(p2) && A.charAt(p2) == B.charAt(p1) && A.substring(p2 + 1).equals(B.substring(p2 + 1));
}
}
}Java
class Solution {
public boolean buddyStrings(String A, String B) {
if (A == null || B == null || A.length() != B.length())
return false;
if (A.equals(B)) {
char[] array = A.toCharArray();
Arrays.sort(array);
int length = array.length;
for (int i = 1; i < length; i++) {
if (array[i] == array[i - 1])
return true;
}
return false;
}
List<Integer> differentIndices = new ArrayList<Integer>();
int length = A.length();
for (int i = 0; i < length; i++) {
char cA = A.charAt(i), cB = B.charAt(i);
if (cA != cB)
differentIndices.add(i);
}
if (differentIndices.size() != 2)
return false;
int index1 = differentIndices.get(0), index2 = differentIndices.get(1);
return A.charAt(index1) == B.charAt(index2) && A.charAt(index2) == B.charAt(index1);
}
}