Package g1501_1600.s1583_count_unhappy_friends

Class Solution

java.lang.Object

g1501_1600.s1583_count_unhappy_friends.Solution

public class Solution
extends Object

1583 - Count Unhappy Friends\. Medium You are given a list of `preferences` for `n` friends, where `n` is always **even**. For each person `i`, `preferences[i]` contains a list of friends **sorted** in the **order of preference**. In other words, a friend earlier in the list is more preferred than a friend later in the list. Friends in each list are denoted by integers from `0` to `n-1`. All the friends are divided into pairs. The pairings are given in a list `pairs`, where pairs[i] = [xi, yi] denotes xi is paired with yi and yi is paired with xi. However, this pairing may cause some of the friends to be unhappy. A friend `x` is unhappy if `x` is paired with `y` and there exists a friend `u` who is paired with `v` but: * `x` prefers `u` over `y`, and * `u` prefers `x` over `v`. Return _the number of unhappy friends_. **Example 1:** **Input:** n = 4, preferences = \[\[1, 2, 3], [3, 2, 0], [3, 1, 0], [1, 2, 0]], pairs = \[\[0, 1], [2, 3]] **Output:** 2 **Explanation:** Friend 1 is unhappy because: - 1 is paired with 0 but prefers 3 over 0, and - 3 prefers 1 over 2. Friend 3 is unhappy because: - 3 is paired with 2 but prefers 1 over 2, and - 1 prefers 3 over 0. Friends 0 and 2 are happy. **Example 2:** **Input:** n = 2, preferences = \[\[1], [0]], pairs = \[\[1, 0]] **Output:** 0 **Explanation:** Both friends 0 and 1 are happy. **Example 3:** **Input:** n = 4, preferences = \[\[1, 3, 2], [2, 3, 0], [1, 3, 0], [0, 2, 1]], pairs = \[\[1, 3], [0, 2]] **Output:** 4 **Constraints:** * `2 <= n <= 500` * `n` is even. * `preferences.length == n` * `preferences[i].length == n - 1` * `0 <= preferences[i][j] <= n - 1` * `preferences[i]` does not contain `i`. * All values in `preferences[i]` are unique. * `pairs.length == n/2` * `pairs[i].length == 2` * xi != yi * 0 <= xi, yi <= n - 1 * Each person is contained in **exactly one** pair.

Constructor Summary

Constructors

Constructor	Description
Solution()

Method Summary

Modifier and Type	Method	Description
int	unhappyFriends(int n, int[][] preferences, int[][] pairs)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Solution

public Solution()

Method Detail

unhappyFriends

public int unhappyFriends(int n,
                          int[][] preferences,
                          int[][] pairs)