LCCI0103-StringToURL.go

package main

// 面试题 01.03. String to URL LCCI
// Write a method to replace all spaces in a string with '%20'. 
// You may assume that the string has sufficient space at the end to hold the additional characters,
// and that you are given the "true" length of the string. 
// (Note: If implementing in Java,please use a character array so that you can perform this operation in place.)

// Example 1:
// Input: "Mr John Smith ", 13
// Output: "Mr%20John%20Smith"

// Example 2:
// Input: "               ", 5
// Output: "%20%20%20%20%20"

// Note:
//     0 <= S.length <= 500000

import "fmt"

func replaceSpaces(S string, length int) string {
    res := []byte{}
    for i := 0; i < len(S); i += 1 {
        // 为 '' 替换成 %20
        if S[i] == ' ' {
            res = append(res,'%')
            res = append(res,'2')
            res = append(res,'0')
        } else {
            res = append(res,S[i])
        }
        if i == length - 1 {
            break
        }
    }
    return string(res)
}

func replaceSpaces1(S string, length int) string {
    bs := []byte(S)
    j := len(bs) - 1
    for i := length - 1; i >= 0; i-- {
        if bs[i] == ' ' {
            bs[j] = '0'
            bs[j - 1] = '2'
            bs[j - 2] = '%'
            j -= 3
        } else {
            bs[j] = bs[i]
            j--
        }
    }
    return string(bs[j+1:])
}

func main() {
    // Example 1:
    // Input: "Mr John Smith ", 13
    // Output: "Mr%20John%20Smith"
    fmt.Println(replaceSpaces("Mr John Smith ", 13)) // "Mr%20John%20Smith"
    // Example 2:
    // Input: "               ", 5
    // Output: "%20%20%20%20%20"
    fmt.Println(replaceSpaces("               ", 5)) // "%20%20%20%20%20"

    fmt.Println(replaceSpaces1("Mr John Smith ", 13)) // "Mr%20John%20Smith"
    fmt.Println(replaceSpaces1("               ", 5)) // "%20%20%20%20%20"
}