leetcode-117 Populating Next Right Pointers in Each Node II

Given a binary tree

struct Node {
  int val;
  Node *left;
  Node *right;
  Node *next;
}

Populate each next pointer to point to its next right node. If there is no next right node, the next pointer should be set to NULL.

Initially, all next pointers are set to NULL.

Example:

leetcode-117 Populating Next Right Pointers in Each Node II

Input: {"$id":"1","left":{"$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":{"$id":"5","left":null,"next":null,"right":{"$id":"6","left":null,"next":null,"right":null,"val":7},"val":3},"val":1}

Output: {"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":{"$id":"4","left":null,"next":{"$id":"5","left":null,"next":null,"right":null,"val":7},"right":null,"val":5},"right":null,"val":4},"next":{"$id":"6","left":null,"next":null,"right":{"$ref":"5"},"val":3},"right":{"$ref":"4"},"val":2},"next":null,"right":{"$ref":"6"},"val":1}

Explanation: Given the above binary tree (Figure A), your function should populate each next pointer to point to its next right node, just like in Figure B.

Note:

You may only use constant extra space.
Recursive approach is fine, implicit stack space does not count as extra space for this problem.

这题解法与116一致，直接运用广度便可以实现，如下：

/*
// Definition for a Node.
class Node {
public int val;
public Node left;
public Node right;
public Node next;

public Node() {}

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){
return null;
}
Queue<Node> nodes = new LinkedList<>();
nodes.add(root);
while(!nodes.isEmpty()) {
   int size = nodes.size();
   while(size > 0) {
       Node tmp = nodes.poll();
       size --;
       if(size == 0) {
           tmp.next = null;
       }else {
           tmp.next = nodes.peek();
       }
       if(tmp.left != null) nodes.add(tmp.left);
       if(tmp.right != null) nodes.add(tmp.right);
   }
}
return root;
}
}

leetcode-117 Populating Next Right Pointers in Each Node II

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