C++有效的括号完整代码

应该比较容易理解，完整代码如下：

#include 
#include 
#include 
#include 
using namespace std;

bool isValid(string s)
{
   stacksta;
   for (int i = 0; i < s.length(); i++)
   {
      if (s[i] == '(' || s[i] == '[' || s[i] == '{')
         sta.push(s[i]);
      else
         if (sta.empty() == true)
            return false;
         else{
            if (sta.top() == '(' && s[i] == ')')
               sta.pop();
            else if (sta.top() == '[' && s[i] == ']')
               sta.pop();
            else if (sta.top() == '{' && s[i] == '}')
               sta.pop();
            else
               return false;
         }
   }
   if (sta.empty() == true)
      return true;
   else
      return false;
}


int main()
{

   string s1 = "()", 
      s2 = "()[]{}", 
      s3 = "(]", 
      s4 = "([)]", 
      s5 = "{[]}";
   cout << isValid(s1) << endl 
        << isValid(s2) << endl 
        << isValid(s3) << endl 
        << isValid(s4) << endl 
        << isValid(s5) << endl;
   system("pause");
}