吐泡泡题解

栈的基本应用
如果栈中没有元素的话就直接进栈就好了
如果栈顶有元素为o并且当前元素也为o的话,就要出栈并且看看之前的是不是O,如果是的话再出栈,不是得话就让O进栈。
如果都为O的话就出栈，最后合并即可。

import java.math.*;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StreamTokenizer;
import java.util.*;
public class Main {
    public static void main(String args[])throws IOException
    {
        StreamTokenizer in = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
        PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
        Scanner input = new Scanner(System.in);
        Stack<Character> stack = new Stack<>();
        while(input.hasNext())
        {
        String s  = input.next();
        for(int i=0;i<s.length();i++)
        {
            if(stack.size()==0)
                stack.add(s.charAt(i));
            else
            {
                if(stack.peek()=='o'&&s.charAt(i)=='o')
                {
                    stack.pop();
                    if(stack.size()!=0&&stack.peek()=='O')
                        stack.pop();
                    else{
                         stack.add('O');
                    }

                }
                else{
                    if(stack.peek()=='O'&&s.charAt(i)=='O')
                {
                    stack.pop();
                }
                    else{
                         stack.add(s.charAt(i));
                    }
                }
            }
        }
        String s1="";
        while(stack.size()!=0)
        {
            s1 = stack.pop()+s1;
        }
        System.out.println(s1);
        }
    }
                  }