Educational Codeforces Round 19 C

Description

Petya recieved a gift of a string s with length up to 105 characters for his birthday. He took two more empty strings t and u and decided to play a game. This game has two possible moves:

• Extract the first character of s and append t with this character.
• Extract the last character of t and append u with this character.

Petya wants to get strings s and t empty and string u lexigraphically minimal.

You should write a program that will help Petya win the game.

Input

First line contains non-empty string s (1 ≤ |s| ≤ 10⁵), consisting of lowercase English letters.

Output

Print resulting string u.

Examples

input

cab

output

abc

input

acdb

output

abdc
题意：第一个字符串的首字母放在第二个字符串的中，第二个字符串的结尾再输出，求能够得到字典序最小的字符串
解法：模拟，如果第一个字符串的首字母为最小，则直接输出，否则压入栈内，处理完毕之后再输出

#include <bits/stdc++.h>
using namespace std;
int num[30];
string s;
int check(char c)
{
    for(int i='a';i<c;i++)
    {
        if(num[i])
        {
            return 0;
        }
    }
    return 1;
}
stack<char>q;
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin>>s;
    for(int i=0;i<s.size();i++)
    {
        num[s[i]]++;
    }
    int cnt=0;
    while(cnt<s.size())
    {
        if(q.empty())
        {
            q.push(s[cnt]);
            num[s[cnt]]--;
            cnt++;
        }
        else if(check(q.top()))
        {
            cout<<q.top();
            q.pop();
        }
        else
        {
            q.push(s[cnt]);
            num[s[cnt]]--;
            cnt++;
        }
    }
    while(!q.empty())
    {
        cout<<q.top();
        q.pop();
    }
    return 0;
}