README_EN.md

01.03. String to URL

中文文档

Description

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"

Explanation: 

The missing numbers are [5,6,8,...], hence the third missing number is 8.

Example 2:

Input: "               ", 5

Output: "%20%20%20%20%20"

 

Note:

1. 0 <= S.length <= 500000

Solutions

Python3

Use replace() function.

class Solution:
    def replaceSpaces(self, S: str, length: int) -> str:
        return S[:length].replace(' ', '%20')

Use list:

class Solution:
    def replaceSpaces(self, S: str, length: int) -> str:
        chars = []
        for c in S[:length]:
            chars.append('%20' if c == ' ' else c)
        return ''.join(chars)

Java

class Solution {
    public String replaceSpaces(String S, int length) {
        char[] chars = S.toCharArray();
        int j = chars.length;
        for (int i = length - 1; i >= 0; --i) {
            if (chars[i] == ' ') {
                chars[--j] = '0';
                chars[--j] = '2';
                chars[--j] = '%';
            } else {
                chars[--j] = chars[i];
            }
        }
        return new String(chars, j, chars.length - j);
    }
}

JavaScript

/**
 * @param {string} S
 * @param {number} length
 * @return {string}
 */
var replaceSpaces = function(S, length) {
    return encodeURI(S.substring(0,length));
};

Go

func replaceSpaces(S string, length int) string {
	// return url.PathEscape(S[:length])
	j := len(S)
	b := []byte(S)
	for i := length - 1; i >= 0; i-- {
		if b[i] == ' ' {
			b[j-1] = '0'
			b[j-2] = '2'
			b[j-3] = '%'
			j -= 3
		} else {
			b[j-1] = b[i]
			j--
		}
	}
	return string(b[j:])
}

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