题解 | 括号的匹配

def is_valid(s):
    pairs = {')': '(', ']': '[', '}': '{', '>': '<'}
    priority = {'<': 1, '(': 2, '[': 3, '{': 4}
    stack = []

    for ch in s:
        if ch in priority:
            # 如果栈不为空，且当前准备进栈的左括号优先级大于栈顶括号的优先级
            if stack and priority[ch] > priority[stack[-1]]:
                return False
            stack.append(ch)
        elif ch in pairs:
            # 如果是右括号，检查是否匹配栈顶的左括号
            if not stack or stack[-1] != pairs[ch]:
                return False
            stack.pop()
    
    
    return len(stack) == 0

T = int(input().strip())
for i in range(T):
    a = is_valid(input().strip())
    if not a:
        print("NO")
    else:
        print("YES")