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
1 #include <bits/stdc++.h> 2 using namespace std; 3 int num[30]; 4 string s; 5 int check(char c) 6 { 7 for(int i='a';i<c;i++) 8 { 9 if(num[i]) 10 { 11 return 0; 12 } 13 } 14 return 1; 15 } 16 stack<char>q; 17 int main() { 18 ios::sync_with_stdio(false); 19 cin.tie(0); 20 cin>>s; 21 for(int i=0;i<s.size();i++) 22 { 23 num[s[i]]++; 24 } 25 int cnt=0; 26 while(cnt<s.size()) 27 { 28 if(q.empty()) 29 { 30 q.push(s[cnt]); 31 num[s[cnt]]--; 32 cnt++; 33 } 34 else if(check(q.top())) 35 { 36 cout<<q.top(); 37 q.pop(); 38 } 39 else 40 { 41 q.push(s[cnt]); 42 num[s[cnt]]--; 43 cnt++; 44 } 45 } 46 while(!q.empty()) 47 { 48 cout<<q.top(); 49 q.pop(); 50 } 51 return 0; 52 }