Medium
On a social network consisting of m
users and some friendships between users, two users can communicate with each other if they know a common language.
You are given an integer n
, an array languages
, and an array friendships
where:
n
languages numbered 1
through n
,languages[i]
is the set of languages the ith
user knows, andfriendships[i] = [ui, vi]
denotes a friendship between the users ui
and vi
.You can choose one language and teach it to some users so that all friends can communicate with each other. Return the minimum number of users you need to teach.
Note that friendships are not transitive, meaning if x
is a friend of y
and y
is a friend of z
, this doesn’t guarantee that x
is a friend of z
.
Example 1:
Input: n = 2, languages = [[1],[2],[1,2]], friendships = [[1,2],[1,3],[2,3]]
Output: 1
Explanation: You can either teach user 1 the second language or user 2 the first language.
Example 2:
Input: n = 3, languages = [[2],[1,3],[1,2],[3]], friendships = [[1,4],[1,2],[3,4],[2,3]]
Output: 2
Explanation: Teach the third language to users 1 and 3, yielding two users to teach.
Constraints:
2 <= n <= 500
languages.length == m
1 <= m <= 500
1 <= languages[i].length <= n
1 <= languages[i][j] <= n
1 <= ui < vi <= languages.length
1 <= friendships.length <= 500
(ui, vi)
are uniquelanguages[i]
contains only unique valuesclass Solution {
fun minimumTeachings(n: Int, languages: Array<IntArray>, friendships: Array<IntArray>): Int {
val m: Int = languages.size
val speak: Array<BooleanArray> = Array(m + 1) { BooleanArray(n + 1) }
val teach: Array<BooleanArray> = Array(m + 1) { BooleanArray(n + 1) }
for (user in 0 until m) {
val userLanguages: IntArray = languages[user]
for (userLanguage: Int in userLanguages) {
speak[user + 1][userLanguage] = true
}
}
val listToTeach: MutableList<IntArray> = ArrayList()
for (friend: IntArray in friendships) {
val userA: Int = friend[0]
val userB: Int = friend[1]
var hasCommonLanguage = false
for (language in 1..n) {
if (speak[userA][language] && speak[userB][language]) {
hasCommonLanguage = true
break
}
}
if (!hasCommonLanguage) {
for (language in 1..n) {
if (!speak[userA][language]) {
teach[userA][language] = true
}
if (!speak[userB][language]) {
teach[userB][language] = true
}
}
listToTeach.add(friend)
}
}
var minLanguage: Int = Int.MAX_VALUE
var languageToTeach = 0
for (language in 1..n) {
var count = 0
for (user in 1..m) {
if (teach[user][language]) {
count++
}
}
if (count < minLanguage) {
minLanguage = count
languageToTeach = language
}
}
val setToTeach: MutableSet<Int> = HashSet()
for (friend: IntArray in listToTeach) {
val userA: Int = friend[0]
val userB: Int = friend[1]
if (!speak[userA][languageToTeach]) {
setToTeach.add(userA)
}
if (!speak[userB][languageToTeach]) {
setToTeach.add(userB)
}
}
return setToTeach.size
}
}