来自:2017年上海金马五校程序设计竞赛(网上资格赛)
Corn's new language
Description
Corn is going to promote programming in the campus, so he wants to add a lot of interesting ideas to make programming more attractive. One task he is working on is to develop a new programming language because he thinks all existing ones are too simple to him. The syntax rules of the language are:
1. () () is a valid program
2. (P) (P) is a valid program, if P P is a valid program
3. PQ PQ is a valid program, if both P P and Q Q are valid programs
Corn wants a compiler for the language. For a program, if it is valid, the compiler should print the max depth in the program. For example " (()) (())" has a depth of 2 2, while " ((())()) ((())())" has a depth of 3 3. Formally, the max depth is the max number of unmatched open brackets in any prefix.
Input
Each case is a non-empty string in a single line, the string will only contain ' ( (' or ' ) )', its length will be no more than 100 100.
Output
For each case, output "YES" and the integer required above if the program is valid, separated with a space. Or "NO" if the program is invalid.
Sample Input
( ) () (()) ((())()) ()) ((
Sample Output
NO NO YES 1 YES 2 YES 3 NO NO
Author: Tianyi Chen
思路:
简单的括号匹配问题,栈解决
代码:
#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<cstdlib>
#include<stack>
using namespace std;
int main()
{
char s[1000000];
while(cin>>s)
{
stack<char>st;
bool flag=1;
int maxn=0;
int len=strlen(s);
for(int i=0;i<len;i++){
if(s[i]=='('){
st.push(s[i]);
if(maxn<st.size()){
maxn=st.size();
}
}
if(s[i]==')'){
if(st.size()<=0){
flag=0;
break;
}
st.pop();
}
}
if(st.size()>0)cout<<"NO"<<endl;
else if(flag==0)cout<<"NO"<<endl;
else{
cout<<"YES "<<maxn<<endl;
}
}
return 0;
}