SCAN电梯调度算法

采用StringBuilder构造栈的方式

import java.util.Scanner;

public class Main{
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        String s = in.nextLine();
        StringBuilder sb = new StringBuilder(s.length());
        int j=-1;
        for(int i=0; i<s.length(); ++i){
          // 不相等，放入“栈”
            if(j==-1 || sb.charAt(j)!=s.charAt(i)){
                sb.append(s.charAt(i));
                j++;
            } else {
              // "出栈"
                sb.deleteCharAt(j--);
            }
        }
        
        System.out.println((sb.length()!=0?sb.toString():0));
    }
}