valid-parentheses

【题目描述】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.

【解题思路】利用栈配对检查

【考查内容】栈，字符串

class Solution {
public:
    bool isValid(string s) {
        stack<char> st;
        for(char c : s){
            if(c == '('|| c == '{' || c == '['){
                st.push(c);
            }else{
                if(st.empty()) return false;
                if(c == ')' && st.top() != '(') return false;
                if(c == '}' && st.top() != '{') return false;
                if(c == ']' && st.top() != '[') return false;
                st.pop();
            }
        }
        return st.empty();
    }
};