765. Couples Holding Hands

765. Couples Holding Hands(1st).java

bhh

765. Couples Holding Hands(2nd).java

    public int minSwapsCouples(int[] row) {
        Map<Integer, Integer> map = new HashMap<>();
        Set<Integer> visited = new HashSet<>(); 
        // record the index of row
        for (int i = 0; i < row.length; i++) {
            map.put(row[i], i);
        }
        int count = 0;
        for (int i = 0; i < row.length; i += 2) {
            if (!visited.contains(i)) { 
                int loop = 0; int cur = i;
                while (!visited.contains(cur)) {
                    visited.add(cur);
                    int first = map.get(row[cur] ^ 1);
                    visited.add(first);
                    cur = first ^ 1;
                    loop ++;
                }
                count += loop - 1;
            }
        }
        return count;
    }