• 116. 填充每个节点的下一个右侧节点指针


    给定一个完美二叉树,其所有叶子节点都在同一层,每个父节点都有两个子节点。二叉树定义如下:

    struct Node {
    int val;
    Node *left;
    Node *right;
    Node *next;
    }
    填充它的每个 next 指针,让这个指针指向其下一个右侧节点。如果找不到下一个右侧节点,则将 next 指针设置为 NULL。

    初始状态下,所有 next 指针都被设置为 NULL。

    示例:

    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。
     

    提示:

    你只能使用常量级额外空间。
    使用递归解题也符合要求,本题中递归程序占用的栈空间不算做额外的空间复杂度。

    画下图很容易理解

    /*
    // Definition for a Node.
    class Node {
        public int val;
        public Node left;
        public Node right;
        public Node next;
    
        public Node() {}
        
        public Node(int _val) {
            val = _val;
        }
    
        public Node(int _val, Node _left, Node _right, Node _next) {
            val = _val;
            left = _left;
            right = _right;
            next = _next;
        }
    };
    */
    
    class Solution {
        public Node connect(Node root) {
            if(root==null||root.left==null)return root;
            root.left.next=root.right;
            if(root.next!=null)
                root.right.next=root.next.left;
            connect(root.left);
            connect(root.right);
            return root;
        }
    }

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  • 原文地址:https://www.cnblogs.com/xxxsans/p/13821385.html
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