20-有效的括号2

第二种解法：使用HashMap简化代码 //使用hashMap将括号存入map中。key为右括号，value为左括号 Map pairs = new HashMap() { { put(')','('); put(']','['); put(']','['); } }; //初始化栈 Deque stack = new LinkedList(); for(int i = 0;i < n;i++) { char ch = s.charAt(i); if(pairs.containsKey(ch)) { if(stack.isEmpty() || stack.peek() != pairs.get(ch)) { return false; } stack.pop(); }else { stack.push(ch); } } return stack.isEmpty(); }