_1583.java

package com.fishercoder.solutions;

import java.util.HashMap;
import java.util.Map;

public class _1583 {
    public static class Solution1 {
        public int unhappyFriends(int n, int[][] preferences, int[][] pairs) {
            int unhappyFriends = 0;
            Map<Integer, Integer> assignedPair = new HashMap<>();
            for (int[] pair : pairs) {
                assignedPair.put(pair[0], pair[1]);
                assignedPair.put(pair[1], pair[0]);
            }
            for (int[] pair : pairs) {
                if (isUnHappy(pair[1], pair[0], preferences, assignedPair)) {
                    unhappyFriends++;
                }
                if (isUnHappy(pair[0], pair[1], preferences, assignedPair)) {
                    unhappyFriends++;
                }
            }
            return unhappyFriends;
        }

        private boolean isUnHappy(int self, int assignedFriend, int[][] preferences, Map<Integer, Integer> assignedPairs) {
            int[] preference = preferences[self];
            int assignedFriendPreferenceIndex = findIndex(preference, assignedFriend);
            for (int i = 0; i <= assignedFriendPreferenceIndex; i++) {
                int preferredFriend = preference[i];
                int preferredFriendAssignedFriend = assignedPairs.get(preferredFriend);
                if (preferredFriendAssignedFriend == self) {
                    return false;
                }
                int candidateAssignedFriendIndex = findIndex(preferences[preferredFriend], preferredFriendAssignedFriend);
                if (isPreferred(self, preferences[preferredFriend], candidateAssignedFriendIndex)) {
                    return true;
                }
            }
            return false;
        }

        private boolean isPreferred(int self, int[] preference, int boundary) {
            for (int i = 0; i <= boundary; i++) {
                if (self == preference[i]) {
                    return true;
                }
            }
            return false;
        }

        private int findIndex(int[] preference, int assignedFriend) {
            for (int i = 0; i < preference.length; i++) {
                if (preference[i] == assignedFriend) {
                    return i;
                }
            }
            return 0;
        }
    }
}