05. 替换空格

链接

​​​https://leetcode-cn.com/problems/ti-huan-kong-ge-lcof/​​​

难度： #简单

题目

请实现一个函数，把字符串 s 中的每个空格替换成"%20"。

​示例 1：​

输入：s = "We are happy."
输出："We%20are%20happy."

​限制：​​0 <= s 的长度 <= 10000​​

代码框架

class Solution {
public String replaceSpace(String s) {

}
}

题目解析

​解答思路1：​

使用Sring自带的replace方法，

替换空格为目标字符串。

​解答思路2：​

按照顺序读取String的char字符，

判断每个char是否为空格，

替换空格为目标字符串。

同时使用StringBuilder拼接返回值。

读取String的char字符相关API:

public char charAt(int index)
public char[] toCharArray()

测试用例

package edu.yuwen.sowrd.num05.solution;

import org.junit.jupiter.api.Assertions;
import org.junit.jupiter.api.Test;

import edu.yuwen.sowrd.num05.sol2.Solution;

public class SolutionTest {
/**
* 输入：s = "We are happy."
* 输出："We%20are%20happy."
*/
@Test
public void testCase1() {
Solution solution = new Solution();
String s = "We are happy.";
String res = solution.replaceSpace(s);
Assertions.assertEquals("We%20are%20happy.", res);

}
}

解答1 推荐

package edu.yuwen.sowrd.num05.sol1;

public class Solution {
public String replaceSpace(String s) {
String res = s.replace(" ", "%20");
return res;
}
}

解答2

package edu.yuwen.sowrd.num05.sol2;

public class Solution {
public String replaceSpace(String s) {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
if (c == ' ') {
sb.append("%20");
} else {
sb.append(c);
}
}
return sb.toString();
}
}