LeetCode演算法題之Valid Parentheses__演算法

問題描述：

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.

解題思路：

典型的使用壓棧的方式解決的問題。

class Solution {public:    bool isValid(string s) {        stack<char> charStack;        size_t i = 0;        while(i != s.length())        {            char c = s[i];            if (c != ')' && c != '}' && c != ']')            {                charStack.push(c);            }            else            {                if (charStack.size() == 0)                   return false;                char pre = charStack.top();                switch(c)                {                case ')':                    if (pre == '(')                      charStack.pop();                    else                      return false;                    break;                case '}':                    if (pre == '{')                      charStack.pop();                    else                      return false;                    break;                case ']':                    if (pre == '[')                      charStack.pop();                    else                      return false;                    break;                }            }            ++i;        }        if (charStack.size() == 0)           return true;        else return false;    }};