力扣-20题有效的括号（C++）- 栈+哈希

旧城等待， 2023-01-23 08:53 21阅读 0赞

题目链接：[https://leetcode-cn.com/problems/valid-parentheses/][https_leetcode-cn.com_problems_valid-parentheses]  
题目如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70 1]

class Solution {
        
    public:
        bool isValid(string s) {
        
            stack<char> stack;
            unordered_map<char,char> hashmap{
        
                {
        '(',')'},{
        '[',']'},{
        '{','}'}
            };
    
            for(auto e:s)
            {
        
                char right=e;
                if(e=='('||e=='['||e=='{'){
        //左括号
                    stack.push(e);
                }
                else if(stack.empty()==false){
        //右括号
                    char left=stack.top();
                    if(hashmap[left]==right){
        
                        stack.pop();
                    }
                    else{
        
                        return false;
                    }
                }else{
        
                    return false;
                } 
            }
            return stack.empty();
    
            /*stack<char> stk;//大宝的
            unordered_map<char,char> unmap{
                {'(',')'},{'[',']'},{'{','}'}
            };
            for (auto e : s) {
                if (e == '[' || e == '(' || e == '{') {
                    stk.push(unmap[e]);
                }
                else if (e == ']' || e == ')' || e == '}') {
                    if (stk.size() && stk.top() == e) {
                        stk.pop();
                    }
                    else {
                        return false;
                    }
                }
            }
            return stk.empty();*/
        }
    };

**tip：**  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70 2]

[https_leetcode-cn.com_problems_valid-parentheses]: https://leetcode-cn.com/problems/valid-parentheses/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70]: /images/20221004/971929485cf946838a8ba28016b69474.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70 1]: /images/20221004/21d17668e0a64efe9fe8ef0241976e3e.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQwNDY3Njcw_size_16_color_FFFFFF_t_70 2]: /images/20221004/23351757753e41e99cdcfdc67668b107.png