Overview

An array is given in which every element is present twice except one element. The objective is to find that element in constant extra space

Example 1

Input: [2, 1, 2, 3, 3]
Output: 1

Example 2

Input: [1, 1, 4]
Output: 4

The idea is to use XOR here. Here we will use two properties of XOR

• XOR of a number with itself is 0

• XOR of 0 and any number is that number

So the idea is to do an XOR of all the numbers in the array. The number that we obtain at the end will be the answer.

Program

Below is the program for the same

package main
import "fmt"
func singleNumber(nums []int) int {
lenNums := len(nums)
res := 0
for i := 0; i < lenNums; i++ {
res = res ^ nums[i]
}
return res
}
func main() {
output := singleNumber([]int{2, 1, 2, 3, 3})
fmt.Println(output)
output = singleNumber([]int{1, 1, 4})
fmt.Println(output)
}

Output:

1
4

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Also if you are interested in understanding how all design patterns can be implemented in Golang. If yes, then this post is for you - All Design Patterns Golang

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