How to change 12345 to 54321? With a string, you can change the string to a rune, and reverse it, but you cannot do the same for an integer. I have searched and found no one talking about this. Examples131415 >>> 5141311357 >>> 7531123a >>> ERROR
-EDIT-
I was thinking, why not create a slice and index that?
Then I realized that you can't index int
(http://play.golang.org/p/SUSg04tZsc)
MY NEW QUESTION IS
How do you index an int? OR
How do you reverse a int?
Here is a solution that does not use indexing an int
package main
import (
"fmt"
)
func reverse_int(n int) int {
new_int := 0
for n > 0 {
remainder := n % 10
new_int *= 10
new_int += remainder
n /= 10
}
return new_int
}
func main() {
fmt.Println(reverse_int(123456))
fmt.Println(reverse_int(100))
fmt.Println(reverse_int(1001))
fmt.Println(reverse_int(131415))
fmt.Println(reverse_int(1357))
}
Result:
654321
1
1001
514131
7531
I converted the integer to a string, reverse the string, and convert the result back to a string.
package main
import (
"fmt"
"strconv"
)
func main() {
fmt.Println(reverse_int(123456))
fmt.Println(reverse_int(100))
fmt.Println(reverse_int(1001))
fmt.Println(reverse_int(131415))
fmt.Println(reverse_int(1357))
}
func reverse_int(value int) int {
intString := strconv.Itoa(value)
newString := ""
for x := len(intString); x > 0; x-- {
newString += string(intString[x - 1])
}
newInt, err := strconv.Atoi(newString)
if(err != nil){
fmt.Println("Error converting string to int")
}
return newInt
}
Very similar to the first answer but this checks to make sure you don't go out of bounds on the type.
func reverse(x int) int {
rev := 0
for x != 0 {
pop := x % 10
x /= 10
if rev > math.MaxInt32/10 || (rev == math.MaxInt32 /10 && pop > 7) {
return 0
}
if rev < math.MinInt32/10 || (rev == math.MinInt32/10 && pop < -8) {
return 0
}
rev = rev * 10 + pop
}
return rev
}