Reverse a number or an integer in Go (Golang)

Overview

The objective is to reverse a number that is an integer. Integer can be negative as well. Some examples

Input: 123
Output: 321
Input: 140
Output: 41
Input: -123
Output: -321
Input: 0
Output: 0

Here is the strategy

• First, make the input number positive

• Use the below logic to iterate over the number and get the last digit every time. Use the last digit to create the reversedDigit

for x > 0 {
lastDigit := x % 10
reversedDigit = reversedDigit*10 + lastDigit
x = x / 10
}

Here is the complete program for the same.

Program

package main
import (
"fmt"
"math"
)
func main() {
reversedInteger := reverse(123)
fmt.Println(reversedInteger)
reversedInteger = reverse(140)
fmt.Println(reversedInteger)
reversedInteger = reverse(-123)
fmt.Println(reversedInteger)
reversedInteger = reverse(0)
fmt.Println(reversedInteger)
}
func reverse(x int) int {
sign := "positive"
if x >= 0 {
sign = "positive"
} else {
sign = "negative"
}
x = int(math.Abs(float64(x)))
var reversedDigit int
for x > 0 {
lastDigit := x % 10
reversedDigit = reversedDigit*10 + lastDigit
x = x / 10
}
if sign == "negative" {
reversedDigit = reversedDigit * -1
}
return reversedDigit
}

Output

321
41
-321
0