0110-balanced-binary-tree.swift

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 * public var val: Int
 * public var left: TreeNode?
 * public var right: TreeNode?
 * public init() { self.val = 0; self.left = nil; self.right = nil; }
 * public init(_ val: Int) { self.val = val; self.left = nil; self.right = nil; }
 * public init(_ val: Int, _ left: TreeNode?, _ right: TreeNode?) {
 * self.val = val
 * self.left = left
 * self.right = right
 * }
 * }
 */
classSolution{
func getMaxHeight(of root:TreeNode?)->Int{
guardlet root = root else{return0}
return1+ max(
getMaxHeight(of: root.left),
getMaxHeight(of: root.right)
)
}

func isBalanced(_ root:TreeNode?)->Bool{
guardlet root = root else{returntrue}

letleftHeight=getMaxHeight(of: root.left)
letrightHeight=getMaxHeight(of: root.right)
letdifference=abs(leftHeight - rightHeight)

 // early exits
guard difference <=1else{returnfalse}
guardisBalanced(root.left)==trueelse{returnfalse}
guardisBalanced(root.right)==trueelse{returnfalse}

returntrue
}
}