7. 整数反转

7. 整数反转

栈理论

package main
import (
    "fmt"
    "math"
)
func reverse(x int) int {
   var stack []int
   for x!=0{
          r :=x%10
          stack = append(stack,r)
          x =x/10
   }
   var r int
   index :=0
   for len(stack)>0{
          top :=stack[len(stack)-1]
          stack = stack[:len(stack)-1]
       r = int(math.Pow10(index))*top+r
          index++
   }
   // 边界
    if !( -(1<<31) <= r && r <= (1<<31)-1) {
        return 0
    }
   return r
}
func main() {
    fmt.Println(reverse(-1234))
    fmt.Println(reverse(120))
    fmt.Println(reverse(1534236469))
}

原地反转

func reverse(x int) int {

    var y =0
    for x!=0{
        y =y*10+x%10
        if !( -(1<<31) <= y && y <= (1<<31)-1) {
            return 0
        }
        x =x/10
    }
    return y
}
func main() {
    fmt.Println(reverse(-1234))
    fmt.Println(reverse(120))
    fmt.Println(reverse(1534236469))
}