FindLuckyIntegerInArray1394.kt

package easy

/*
Given an array of integers arr, a lucky integer is an integer which has a frequency in the array equal to its value.

Return a lucky integer in the array. If there are multiple lucky integers return the largest of them. If there is no lucky integer return -1.

Example 1:

Input: arr = [2,2,3,4]
Output: 2
Explanation: The only lucky number in the array is 2 because frequency[2] == 2.
Example 2:

Input: arr = [1,2,2,3,3,3]
Output: 3
Explanation: 1, 2 and 3 are all lucky numbers, return the largest of them.
Example 3:

Input: arr = [2,2,2,3,3]
Output: -1
Explanation: There are no lucky numbers in the array.
Example 4:

Input: arr = [5]
Output: -1
Example 5:

Input: arr = [7,7,7,7,7,7,7]
Output: 7
 */
fun findLucky(arr: IntArray): Int {
    val map=HashMap<Int,Int>()

    // map unique item array with occurrences˚
    arr.forEach{
        map[it]=(map[it]?:0) +1
    }
    var max=Int.MIN_VALUE

    map.forEach{
     if(it.key==it.value&& it.key>max)
     {
         max=it.key
     }
    }
    return if(max!= Int.MIN_VALUE)
        max
    else
        -1
}