剑指 Offer 05. 替换空格

/**
 * @Class ReplaceSpace
 * @Description 剑指 Offer 05. 替换空格
 * 请实现一个函数，把字符串 s 中的每个空格替换成"%20"。
 * <p>
 * 示例 1：
 * 输入：s = "We are happy."
 * 输出："We%20are%20happy."
 * <p>
 * 限制：
 * 0 <= s 的长度 <= 10000
 * @Author
 * @Date 2020/6/28
 **/
public class ReplaceSpace {  
}

// 简单方式直接字符串替换 
public static String replaceSpace(String s) {
        if (s == null || s.length() == 0) return s;

        StringBuilder ans = new StringBuilder("");
        for (int i = 0; i < s.length(); i++) {
            char ch = s.charAt(i);
            if (ch == ' ') {
                ans.append("%20");
            } else ans.append(ch);
        }
        return ans.toString();
    }

   /**
    *  java 中没有结束符，是通过s.length 来找到字符串结尾的，redis的sds 也是通过length属性找到字符串结尾
    */
   /* public static String replaceSpace(String s) {
        if (s == null || s.length() == 0) return s;

        char[] chs = new char[s.length() * 3 + 1];
        int pos = 0;
        for (int i = 0; i < s.length(); i++) {
            char ch = s.charAt(i);
            if (ch != ' ') chs[pos++] = ch;
            else {
                chs[pos++] = '%';
                chs[pos++] = '2';
                chs[pos++] = '0';
            }
        }
        chs[pos] = '';
        return String.valueOf(chs);
    }*/

// 测试用例
public static void main(String[] args) {
	String s = " We are happy.";
	String ans = replaceSpace(s);
	System.out.println("demo01 result:" + ans);
}