LeetCode-in-All

20. Valid Parentheses

Easy

Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

An input string is valid if:

1. Open brackets must be closed by the same type of brackets.
2. Open brackets must be closed in the correct order.

Example 1:

Input: s = “()”

Output: true

Example 2:

Input: s = “()[]{}”

Output: true

Example 3:

Input: s = “(]”

Output: false

Example 4:

Input: s = “([)]”

Output: false

Example 5:

Input: s = “{[]}”

Output: true

Constraints:

• 1 <= s.length <= 104
• s consists of parentheses only '()[]{}'.

Solution

func isValid(s string) bool {
	stack := make([]rune, 0)
	for _, c := range s {
		switch c {
		case '(', '[', '{':
			stack = append(stack, c)
		case ')':
			if len(stack) == 0 || stack[len(stack)-1] != '(' {
				return false
			}
			stack = stack[:len(stack)-1]
		case '}':
			if len(stack) == 0 || stack[len(stack)-1] != '{' {
				return false
			}
			stack = stack[:len(stack)-1]
		case ']':
			if len(stack) == 0 || stack[len(stack)-1] != '[' {
				return false
			}
			stack = stack[:len(stack)-1]
		}
	}

	return len(stack) == 0
}

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