SingleNumber136.kt

package easy

/**
 * Given a non-empty array of integers nums, every element appears twice except for one. Find that single one.

You must implement a solution with a linear runtime complexity and use only constant extra space.



Example 1:

Input: nums = [2,2,1]
Output: 1
Example 2:

Input: nums = [4,1,2,1,2]
Output: 4
Example 3:

Input: nums = [1]
Output: 1


Constraints:

1 <= nums.length <= 3 * 104
-3 * 104 <= nums[i] <= 3 * 104
Each element in the array appears twice except for one element which appears only once.
 */
fun singleNumber(nums: IntArray): Int {
    val map = HashMap<Int,Int>()

    nums.forEach { num->
        map[num]= (map[num]?:0)+1
    }

    for (entry in map.entries)
    {
        if(entry.value==1)
            return entry.key
    }

return -1
}
// TC is O(N) and SC O(1)
fun singleNumberSol2(nums: IntArray): Int {
     var result = 0
    for(i in 0 until  nums.size)
        result=result.xor(nums[i])


    return result
}