题解 | 整数与IP地址间的转换

package main

import (
	"fmt"
	"strconv"
	"strings"
)

func strToInt(str string) int {
	v, _ := strconv.Atoi(str)
	return v
}

func main() {
	for {
		var input string
		fmt.Scan(&input)

		if len(input) == 0 {
			break
		}

		arr0 := strings.Split(input, ".")
		// fmt.Printf("%#v\n", arr0)

		if len(arr0) == 4 { // ip
			val := (strToInt(arr0[0]) << (8 * 3)) +
				(strToInt(arr0[1]) << (8 * 2)) +
				(strToInt(arr0[2]) << (8 * 1)) +
				(strToInt(arr0[3]))
			fmt.Printf("%v\n", val)
		} else { // number
			rawVal := strToInt(input)
			fmt.Printf("%v.%v.%v.%v",
				(rawVal >> (8 * 3) & 255),
				(rawVal >> (8 * 2) & 255),
				(rawVal >> (8 * 1) & 255),
				(rawVal & 255),
			)
		}
	}
}