Mock Interview: Facebook

859. Buddy Strings

class Solution {
    public boolean buddyStrings(String s, String goal) {
        boolean hasSame = false; 
        int[] chars = new int[26];
        if (s.length() != goal.length()) {
            return false;
        }
        
        int pos1 = -1;
        int pos2 = -1; 
        
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) != goal.charAt(i)) {
                if (pos1 != -1 && pos2 != -1) {
                    return false;
                } else if (pos1 == -1) {
                    pos1 = i;
                } else {
                    pos2 = i;
                }
            }
            chars[s.charAt(i) - 'a']++;
            if (chars[s.charAt(i) - 'a'] >= 2) {
                hasSame = true;
            }
        }
        
        if (pos1 == -1 && pos2 == -1) {
            return hasSame; 
        }
        
        if (pos2 == -1) {
            return false; 
        }
        
        return (s.charAt(pos1) == goal.charAt(pos2)) && (s.charAt(pos2) == goal.charAt(pos1));
    }
}

Runtime: 3 ms, faster than 48.93% of Java online submissions for Buddy Strings.
Memory Usage: 38.7 MB, less than 95.53% of Java online submissions for Buddy Strings.

"aa" 이런 케이스들 처음에 풀때 절대 통과 못하는데
인터뷰가 조금 걱정되네유ㅠㅠ
돌려보기전까지 죽어도 생각 안나는 에지케이즈들~~

class Solution {
    public int[][] diagonalSort(int[][] mat) {
        // Store the matrix dimensions
        int m = mat.length;
        int n = mat[0].length;
        
        // Data structure to store the diagonals.
        Map<Integer, Queue<Integer>> diagonals = new HashMap<>();
        
        // Insert values into the HashMap.
        for (int row = 0; row < m; row++) {
            for (int col = 0; col < n; col++) { 
                //row - col: diagonals
                diagonals.putIfAbsent(row - col, new PriorityQueue<>());
                diagonals.get(row - col).add(mat[row][col]);
            }   
        }

        // Take values back out of the HashMap.
        for (int row = 0; row < m; row++) {
            for (int col = 0; col < n; col++) {
                mat[row][col] = diagonals.get(row - col).remove();
            }
        }
        
        return mat;
    }
}

Runtime: 10 ms, faster than 26.77% of Java online submissions for Sort the Matrix Diagonally.
Memory Usage: 39.8 MB, less than 77.97% of Java online submissions for Sort the Matrix Diagonally.

diagonal 같은 애들이 다 같은 row - col이 있다는 점...^^
그거 하나하나 sort 해주고 다시 넣어주는 방식..