LeetCode-剑指offer05.替换空格

标题：剑指offer05.替换空格

题目

示例1

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

限制

0 <= s 的长度 <= 10000

代码Java

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

// 双指针
public String replaceSpace1(String s) {
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < s.length(); i++) {
        if (s.charAt(i) == ' ') {
            sb.append("  ");
        }
    }
    if (sb.length() == 0) return s;
    int left = s.length() - 1;
    s += sb;
    int right = s.length() - 1;
    char[] chars = s.toCharArray();
    while (left >= 0) {
        if (chars[left] == ' ') {
            chars[right--] = '0';
            chars[right--] = '2';
            chars[right--] = '%';
        } else {
            chars[right--] = chars[left];
        }
        left--;
    }
    return new String(chars);
}