forked from neetcode-gh/leetcode
-
Notifications
You must be signed in to change notification settings - Fork 0
/
20-Valid-Parentheses
47 lines (40 loc) · 898 Bytes
/
20-Valid-Parentheses
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
class Solution {
func isValid(_ s: String) -> Bool {
let parenMap:[Character:Character] = ["(":")", "[":"]", "{":"}"]
var stack = Stack<Character>()
for c in s {
if parenMap.keys.contains(c) {
stack.push(c)
} else if stack.isEmpty || c != parenMap[stack.pop()!] {
return false
}
}
return stack.isEmpty
}
}
class Node<T> {
var data: T
var next: Node<T>?
init(_ value: T) {
self.data = value
}
}
class Stack<T> {
var head: Node<T>?
var isEmpty: Bool {
head == nil
}
func peak() -> Node<T>? {
head
}
func push(_ data: T) {
var node = Node<T>(data)
node.next = head
head = node
}
func pop() -> T? {
var data = head?.data
head = head?.next
return data
}
}