20. 有效的括号 @Python @Go

原题

https://leetcode.cn/problems/valid-parentheses/description/

思路

栈

复杂度

时间：O(n)
空间：O(n)

Python代码

class Solution:
    def isValid(self, s: str) -> bool:
        stack = []
        d = {")": "(", "}": "{", "]": "["}

        for i, ch in enumerate(s):
            if ch in ["(", "{", "["]:
                stack.append(ch)
            else:
                if len(stack) == 0 or stack[-1] != d[ch]:
                    return False
                else:
                    stack.pop()
        return len(stack) == 0

Go代码

func isValid(s string) bool {
	stack := []byte{}
	m := map[byte]byte{
		')': '(',
		']': '[',
		'}': '{'}
	for _, ch := range s {
		if ch == '(' || ch == '{' || ch == '[' {
			stack = append(stack, byte(ch))
		} else {
			if len(stack) == 0 || stack[len(stack)-1] != m[byte(ch)] {
				return false
			} else {
				stack = stack[:len(stack)-1]
			}
		}
	}
	return len(stack) == 0
}