内容简介:Total Accepted: 103858 Total Submissions: 355021 Difficulty: EasyGiven a string containing just the characters ‘(‘, ‘)’, ‘{‘, ‘}’, ‘[‘ and ‘]’, determine if the input string is valid.The brackets must close in the correct order, “()” and “()[]{}” are all
Total Accepted: 103858 Total Submissions: 355021 Difficulty: Easy
Given a string containing just the characters ‘(‘, ‘)’, ‘{‘, ‘}’, ‘[‘ and ‘]’, determine if the input string is valid.
The brackets must close in the correct order, “()” and “()[]{}” are all valid but “(]” and “([)]” are not.
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func isValid(_ s: String) -> Bool {
var stack = [Character](), b = true
func compare(_ c: Character) -> Bool {
guard let t = stack.popLast() else { return false }
return (c == ")" && t == "(") || (c == "]" && t == "[" ) || (c == "}" && t == "{")
}
loop: for c in s {
switch c {
case "(", "[", "{":
stack.append(c)
default:
b = compare(c)
if !b { break loop }
}
}
return b && stack.isEmpty
}
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