859. Buddy Strings - LeetCode

Question

859. Buddy Strings

Solution

題目大意:

兩個字符串,其中一個字符串任意兩個字符互換後與另外一個字符串相等,只能互換一次

思路:

diff 記錄不一樣字符數

兩個字符串長度不一樣 return false

兩個字符串長度相同:
abc abd     無重複,diff == 1  ca[3] != cb[3] return false
abc abc     無重複,diff == 0  return false
ab ba       無重複,diff == 2  return true
aa aa       aa重複,diff == 0  return true
aabc aabc   aa重複,diff == 0  return true
aacb aabc   aa重複,diff == 2  return true

Java實現:

public boolean buddyStrings(String A, String B) {
    if (A.length() != B.length()) return false;
    int[] ca = new int[26];
    int[] cb = new int[26];
    int diff = 0;
    for (int i = 0; i < A.length(); i++) {
        ca[A.charAt(i) - 'a']++;
        cb[B.charAt(i) - 'a']++;
        if (A.charAt(i) != B.charAt(i)) diff++;
    }
    for (int i = 0; i < ca.length; i++) {
        if (diff == 0 && ca[i] > 1) return true;
        if (ca[i] != cb[i]) return false;
    }
    return diff == 2;
}