栈的使用以及括号匹配扩展

678. Valid Parenthesis String

Medium

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Given a string containing only three types of characters: '(', ')' and '*', write a function to check whether this string is valid. We define the validity of a string by these rules:

1. Any left parenthesis​​'('​​​ must have a corresponding right parenthesis​​')'​​.
2. Any right parenthesis​​')'​​​ must have a corresponding left parenthesis​​'('​​.
3. Left parenthesis​​'('​​​ must go before the corresponding right parenthesis​​')'​​.
4. ​​'*'​​​ could be treated as a single right parenthesis​​')'​​​ or a single left parenthesis​​'('​​ or an empty string.
5. An empty string is also valid.

Example 1:

Input: "()" Output: True

Example 2:

Input: "(*)" Output: True

Example 3:

Input: "(*))" Output: True

class Solution {
public:
    bool checkValidString(string s) {
        stack<int> Left;
        stack<int> Star;
        for(int i = 0;i < s.length();i ++){
            if(s[i] == '('){
                Left.push(i);
            }
            else if(s[i] == '*'){
                Star.push(i);
            }
            else{
                if(!Left.empty()){
                    Left.pop();
                }
                else if(!Star.empty()){
                    Star.pop();
                }
                else{
                    return false;
                }
            }
        }
        while(!Left.empty() && !Star.empty()){
            if(Left.top() > Star.top()){
                return false;
            }
            Left.pop();Star.pop();
        }
        if(!Left.empty()){return false;}
        else{return true;}
    }
};