Marc Lester Tan

There are multiple ways to solve this problem. One could sort the arrays and check element by element if two consecutive items are equal.

Another approach is to use a list to store elements that has been processed and if indexOf(element) is not -1 then return true. I tried this but it’s slow.

My final solution uses hashmap to keep track of processed elements. This is definitely way faster particulary when the array size is huge.

class Solution {
    fun containsDuplicate(nums: IntArray): Boolean {
        val map = HashSet<Int>()
        nums.forEach {
            if(map.contains(it)) return true            
            map.add(it)
        }
        
        return false
    }
}

Runtime: 228 ms, faster than 83.15% of Kotlin online submissions for Contains Duplicate.
Memory Usage: 38 MB, less than 100.00% of Kotlin online submissions for Contains Duplicate.