package _020_valid_parentheses

// 20. 有效的括号
// https://leetcode-cn.com/problems/valid-parentheses/

func isValid(s string) bool {
	stack := make([]int32, 0, len(s))
	// ( = 40
	// ) = 41
	// { = 123
	// } = 125
	// [ = 91
	// ] = 93
	for _, a := range s {
		if a == 40 || a == 123 || a == 91 {
			stack = append(stack, a)
		} else if a == 41 || a == 125 || a == 93 {
			l := len(stack)
			if l == 0 {
				return false
			}
			pop := stack[l-1]
			if (a == 41 && pop != 40) || (a == 125 && pop != 123) || (a == 93 && pop != 91) {
				return false
			}
			stack = stack[:l-1]
		}
	}

	return len(stack) == 0
}