バイナリハックイージー / Unhappy Hacking (ABC Edit) （stack）

題目鏈接：http://abc043.contest.atcoder.jp/tasks/abc043_b

Time limit : 2sec / Memory limit : 256MB

Score : 200 points

Problem Statement

Sig has built his own keyboard. Designed for ultimate simplicity, this keyboard only has 3 keys on it: the 0 key, the 1 key and the backspace key.

To begin with, he is using a plain text editor with this keyboard. This editor always displays one string (possibly empty). Just after the editor is launched, this string is empty. When each key on the keyboard is pressed, the following changes occur to the string:

• The 0 key: a letter 0 will be inserted to the right of the string.
• The 1 key: a letter 1 will be inserted to the right of the string.
• The backspace key: if the string is empty, nothing happens. Otherwise, the rightmost letter of the string is deleted.

Sig has launched the editor, and pressed these keys several times. You are given a string s, which is a record of his keystrokes in order. In this string, the letter 0 stands for the 0 key, the letter 1 stands for the 1 key and the letter B stands for the backspace key. What string is displayed in the editor now?

Constraints

• 1≦|s|≦10 (|s| denotes the length of s)
• s consists of the letters 0, 1 and B.
• The correct answer is not an empty string.

---

Input

The input is given from Standard Input in the following format:

s

Output

Print the string displayed in the editor in the end.

---

Sample Input 1

Copy

01B0

Sample Output 1

Copy

00

Each time the key is pressed, the string in the editor will change as follows: 0, 01, 0, 00.

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Sample Input 2

Copy

0BB1

Sample Output 2

Copy

1

Each time the key is pressed, the string in the editor will change as follows: 0, (empty), (empty), 1.

題解：棧 我也不知道為啥有三組數據過不了 先放這

  大晚上來補這道題 后來才發現自己的思路錯了 后面輸出的順序完全反了 （棧的特性 最后只需要改改順序就行了）思路錯了居然還過了一大半的數據 有毒 ...

#include <iostream>
#include <algorithm>
#include <cstring>
#include <cstdio>
#include <vector>
#include <cstdlib>
#include <iomanip>
#include <cmath>
#include <ctime>
#include <map>
#include <set>
#include <queue>
#include <stack>
using namespace std;
#define lowbit(x) (x&(-x))
#define max(x,y) (x>y?x:y)
#define min(x,y) (x<y?x:y)
#define MAX 100000000000000000
#define MOD 1000000007
#define pi acos(-1.0)
#define ei exp(1)
#define PI 3.141592653589793238462
#define INF 0x3f3f3f3f3f
#define mem(a) (memset(a,0,sizeof(a)))
typedef long long ll;
ll gcd(ll a,ll b){
    return b?gcd(b,a%b):a;
}
bool cmp(int x,int y)
{
    return x>y;
}
const int N=10005;
const int mod=1e9+7;
int main()
{
    std::ios::sync_with_stdio(false);
    string a;
    cin>>a;
    int len=a.length();
    stack <char> q ;
    for(int i=0;i<len;i++){
        if(a[i]=='1')  q.push('1');
        else if(a[i]=='0')  q.push('0');
        else if(a[i]=='B'){
            if(q.size()>0)
                q.pop();
        }
    }
    char b[20];
    int t=0,i;
    while(q.size()>0){
        b[t++]=q.top();
        q.pop();
    }
    for(i=t-1;i>=0;i--)
        cout<<b[i];
    cout<<endl;
    return 0;
}