Valid Parentheses

Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

The brackets must close in the correct order, "()" and "()[]{}" are all valid but "(]" and "([)]" are not.

用栈会很方便。为了练习vector抽风的没有用栈，很疼……

class Solution {
public:
    bool isValid(string s) {
        if(s.length() == 0)return 1;
        
        vector<char> v;
        
        for(int i = 0 ; i < s.length(); i++)
        {
            if(is(s[i]))
            {
                v.push_back(s[i]);
            }
        }
        if(v.size()%2 ==1)return 0;
        
        while(true)
        {
            int flag = 0;
            for(int i = 0 ; i < v.size()&& v.size() > 0; i++)
            {
                if(v[i] == ')' || v[i] == ']' || v[i] == '}' )
                {
                    if(i == 0)return 0;
                    if(v[i] == ')' &&v[i-1] == '('  ||v[i] == ']' &&v[i-1] == '[' || v[i] == '}' &&v[i-1] == '{'   )
                    {
                        v.erase(v.begin() + i -1 , v.begin() + i +1);
                        
                        break;
                    }
                    else
                    return 0;
                }
                if(v.size() == 0)return 1;
                if(i == v.size() - 1)return 0;
            }
            if(v.size() == 0 )break;
        }
        
        return 1;
        
    }
    
    bool is(char ch)
    {
        if(ch == '(' || ch == ')' || ch == '[' || ch ==']' || ch =='{' || ch =='}')
        return 1;
        else
        return 0;
    }
};