题解 | #动态字符串#
动态字符串
https://www.nowcoder.com/practice/e2c51a6f126b41f9be403376c7adea15
import java.util.Scanner; public class Main { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); String line = scanner.next(); StringBuilder sb = new StringBuilder(line); for (int i = line.length() - 3; i >= 0; i -= 3) { sb.insert(i, ','); } System.out.println(sb); } }