535. Encode and Decode TinyURL #

Problem #

Note: This is a companion problem to the System Design problem: Design TinyURL.

TinyURL is a URL shortening service where you enter a URL such as https://leetcode.com/problems/design-tinyurl and it returns a short URL such as http://tinyurl.com/4e9iAk.

Design the encode and decode methods for the TinyURL service. There is no restriction on how your encode/decode algorithm should work. You just need to ensure that a URL can be encoded to a tiny URL and the tiny URL can be decoded to the original URL.

Problem Summary #

TinyURL is a URL shortening service. For example: when you enter a URL  https://leetcode.com/problems/design-tinyurl, it returns a shortened URL  http://tinyurl.com/4e9iAk.

Requirement: Design the TinyURL encryption encode and decryption decode methods. There is no restriction on how your encryption and decryption algorithms are designed and work. You only need to ensure that a URL can be encrypted into a TinyURL, and that this TinyURL can be restored to the original URL using the decryption method.

Solution Approach #

• Easy problem. Since the problem does not specify the encode() algorithm, there is a lot of freedom. The simplest approach is to store the original URL and record its index position in a string array. During decode(), restore the original URL according to the stored index.

Code #

package leetcode

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

type Codec struct {
	urls []string
}

func Constructor() Codec {
	return Codec{[]string{}}
}

// Encodes a URL to a shortened URL.
func (this *Codec) encode(longUrl string) string {
	this.urls = append(this.urls, longUrl)
	return "http://tinyurl.com/" + fmt.Sprintf("%v", len(this.urls)-1)
}

// Decodes a shortened URL to its original URL.
func (this *Codec) decode(shortUrl string) string {
	tmp := strings.Split(shortUrl, "/")
	i, _ := strconv.Atoi(tmp[len(tmp)-1])
	return this.urls[i]
}

/**
 * Your Codec object will be instantiated and called as such:
 * obj := Constructor();
 * url := obj.encode(longUrl);
 * ans := obj.decode(url);
 */