Overview

An array is given. The objective is to find if there exists any number for which it’s double also exists.

Example 1

Input: [8,5,4,3]
Output: true
Explanation: 4 and 8

Example 2

Input: [1,3,7,9]
Output: false
Explanation: There exists no number for which its double exist

The idea is to use a map here. For every element, we will check  and return true if

• If its double exists in the map

• If the number is even then if its half exists in the map

Program

Below is the program for the same

package main

import "fmt"

func checkIfExist(arr []int) bool {
	numMap := make(map[int]bool)

	for i := 0; i < len(arr); i++ {
		if numMap[arr[i]*2] {
			return true
		}
		if arr[i]%2 == 0 && numMap[arr[i]/2] {
			return true
		}
		numMap[arr[i]] = true
	}
	return false
}

func main() {
	output := checkIfExist([]int{8, 5, 4, 3})
	fmt.Println(output)

	output = checkIfExist([]int{1, 3, 7, 9})
	fmt.Println(output)

}

Output:

true
false

Also, check out our system design tutorial series here – System Design Tutorial Series