g0801_0900.s0859_buddy_strings.Solution Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated

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package g0801_0900.s0859_buddy_strings;

// #Easy #String #Hash_Table #2022_03_27_Time_2_ms_(85.33%)_Space_43.4_MB_(16.33%)

/**
 * 859 - Buddy Strings\.
 *
 * Easy
 *
 * 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 * 10⁴
 * *   `s` and `goal` consist of lowercase letters.
**/
public class Solution {
    public boolean buddyStrings(String s, String goal) {
        int first = -1;
        int second;
        int[] sCounts = new int[26];
        if (s.equals(goal)) {
            for (int i = 0; i < s.length(); i++) {
                sCounts[s.charAt(i) - 'a']++;
                if (sCounts[s.charAt(i) - 'a'] > 1) {
                    return true;
                }
            }
        }
        for (int i = 0; i < s.length(); i++) {
            char curr = s.charAt(i);
            sCounts[curr - 'a']++;
            if (curr != goal.charAt(i)) {
                if (first == -1) {
                    first = i;
                } else {
                    second = i;
                    char[] ss = s.toCharArray();
                    char temp = ss[first];
                    ss[first] = ss[second];
                    ss[second] = temp;
                    return String.valueOf(ss).equals(goal);
                }
            }
        }
        return false;
    }
}