/*
 * CC 150 1.2 Reverse A string
 * Created By Scarlett
 * Time: 12/19/2014 Fri 7:43 AM
 * 题目要求用C/C++,我们都是用java的，就简单理解成reverse a string吧
 * 注意题目中function return的是void, 所以reverse后的string要赋给原来的string
 * 用于测试时，不妨在method最后添一句system.out.println(s)
 *
 */
public class Reverse {
	/*
	 * 思路1：StringBuffer本身就有reverse method
	 */
   public void reverse1(String s) {
	   if (s==null) return;
	   StringBuffer sb = new StringBuffer(s);
	   sb.reverse();
	   s = sb.toString();

   }
   /*
    * 这是最直观的reverse,但感觉不太好。
    * swap了len/2次，每次生成四个新string..感觉开销太大
    */
   public void reverse(String s) {
	   if (s==null) return;
	   int len = s.length();
	   for (int i=0; i<len/2; i++) {
		   char temp = s.charAt(i);
		   char reverse = s.charAt(len-i-1);
		   s =s.substring(0, i)+reverse+s.substring(i+1, len-i-1)+temp+s.substring(len-i);
	   }
	   System.out.println(s);
   }
   /*
    * 思路3：转成charArray,再swap
    * 交换了len/2次
    */
   public void reverse3(String s) {
	   if (s==null) return;
	   char[] cArray = s.toCharArray();
	   int len = cArray.length;
	   for (int i=0; i<len/2; i++) {
		   //Swap c[i] and c[len-i-1]
		  char temp = cArray[i];
		  cArray[i]= cArray[len-i-1];
		  cArray[len-i-1] = temp;
	   }
   }
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Reverse s= new Reverse();
		s.reverse("Yes, we can.");
	    s.reverse("good.");
	    s.reverse("great!");
		s.reverse("");
		s.reverse(null);

	}

}