leetcode-709-easy

To Lower Case
思路一: 遍历，遇到 A-Z 范围内的 char 转换到对应 a-z 范围

public String toLowerCase(String s) {
    if (s == null || s.isEmpty()) return s;
    int gap = 'a' - 'A';

    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < s.length(); i++) {
        if (s.charAt(i) >= 'A' && s.charAt(i) <= 'Z') {
            sb.append((char)(s.charAt(i) + gap));
        } else {
            sb.append(s.charAt(i));
        }
    }

    return sb.toString();
}