有效的括号

有效的括号

思路：我们先创建一个栈，让左括号入栈，与右括号判断

Stack stack=new Stack<>();

将字符串中的符号转化为字符

char ch = s.charAt(i);

完整代码如下：

class Solution {public boolean isValid(String s) {if (s == null) return false;Stack<Character> stack=new Stack<>();for (int i = 0; i < s.length(); i++) {char ch = s.charAt(i);if (ch == '(' || ch == '{' || ch == '[') {stack.push(ch);} else {//情况2if (stack.empty()) {return false;}char topL = stack.peek();if (topL == '(' && ch == ')' || topL == '{' && ch == '}' || topL == '[' && ch == ']') {stack.pop();} else {return false;}}}//情况3if(!stack.empty()){return false;}return true;}
}