Disclaimer: This article is a blogger original article, shall not be reproduced without the bloggers allowed. https://blog.csdn.net/huanglinxiao/article/details/91453161
Includes only a given '(', ')' string, '{', '}', '[', ']', and determine whether the string is valid.
Valid string must meet:
Left bracket must be closed by a closing parenthesis of the same type.
Left parenthesis must be closed in the correct order.
Note the empty string can be considered a valid string.
Example 1:
Input: "()"
Output: true
Example 2:
Input: "() [] {}"
Output: true
Example 3:
Input: "(]"
Output: false
solution:
func isValid(_ s: String) -> Bool {
var stack = [Character]()
for char in s {
if char == "(" || char == "[" || char == "{" {
stack.append(char)
} else if char == ")" {
guard stack.count != 0 && stack.removeLast() == "(" else {
return false
}
} else if char == "]" {
guard stack.count != 0 && stack.removeLast() == "[" else {
return false
}
} else if char == "}" {
guard stack.count != 0 && stack.removeLast() == "{" else {
return false
}
}
}
return stack.isEmpty
}