leetcode-116-填充每个节点的下一个右侧节点指针
题目描述:
输入:{"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":null,"right":null,"val":4},"next":null,"right":{"$id":"4","left":null,"next":null,"right":null,"val":5},"val":2},"next":null,"right":{"$id":"5","left":{"$id":"6","left":null,"next":null,"right":null,"val":6},"next":null,"right":{"$id":"7","left":null,"next":null,"right":null,"val":7},"val":3},"val":1} 输出:{"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":{"$id":"4","left":null,"next":{"$id":"5","left":null,"next":{"$id":"6","left":null,"next":null,"right":null,"val":7},"right":null,"val":6},"right":null,"val":5},"right":null,"val":4},"next":{"$id":"7","left":{"$ref":"5"},"next":null,"right":{"$ref":"6"},"val":3},"right":{"$ref":"4"},"val":2},"next":null,"right":{"$ref":"7"},"val":1} 解释:给定二叉树如图 A 所示,你的函数应该填充它的每个 next 指针,以指向其下一个右侧节点,如图 B 所示。
方法一:递归:
class Solution: def connect(self, root: 'Node') -> 'Node': if not root: return if root.left: root.left.next = root.right if root.next: root.right.next = root.next.left self.connect(root.left) self.connect(root.right) return root
方法二:迭代:
class Solution: def connect(self, root: 'Node') -> 'Node': pre = root while pre: cur = pre while cur: if cur.left: cur.left.next = cur.right if cur.right and cur.next: cur.right.next = cur.next.left cur = cur.next pre = pre.left return root