Leetcode(19)

https://leetcode.com/problems/valid-parentheses/#/description

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.

Solution:

经典的匹配题，用stack来解决。

bool ValidParentheses::isValid(std::string s) {    std::stack<char> leftParentheses;    for (char c : s) {        if (c == '(' || c == '[' || c == '{') {            leftParentheses.push(c);        } else if (c == ')' || c == ']' || c == '}') {            char leftParenthese = ' ';            switch (c) {                case ')':                    leftParenthese = '(';                    break;                case ']':                    leftParenthese = '[';                    break;                case '}':                    leftParenthese = '{';                    break;            }            if(leftParentheses.empty() || leftParentheses.top() != leftParenthese) {                return false;            }            leftParentheses.pop();        }    }    return leftParentheses.empty();}