import java.util.*; public class Transform { public String trans(String s, int n) { // write code here s = s.substring(0,n); String[] temp = s.split(" +"); StringBuilder res = new StringBuilder(); char tempChar; for (int i = temp.length-1; i >= 0 ;i--){ for (int j = 0; j < temp[i].length() ; j++){ tempChar = temp[i].charAt(j); if (Character.isLowerCase(tempChar)) res.append(Character.toUpperCase(tempChar)); else if (Character.isUpperCase(tempChar)) res.append(Character.toLowerCase(tempChar)); } if (i!=0) res.append(" "); } return res.toString(); } } 求问第一题代码哪里错了。。一直不能AC。。第三题也是_(:зゝ∠)_