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You are given a perfect binary tree where all leaves are on the same level, and every parent has two children. The binary tree has the following definition:
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:
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":{"$id":"5","left":{"$id":"6","left":null,"next":null,"right":null,"val":6},"next":null,"right":{"$id":"7","left":null,"next":null,"right":null,"val":7},"val":3},"val":1} Output: {"$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} Explanation: Given the above perfect binary tree (Figure A), your function should populate each next pointer to point to its next right node, just like in Figure B.
题目大意:
给出一个完美二叉树。将同一水平线上的节点连接起来作为节点的next。
解题思路:
使用队列完美解决。
/*
// Definition for a Node.
class Node {
public:
int val;
Node* left;
Node* right;
Node* next;
Node() {}
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 root;
deque<Node*> c;
c.push_back(root);
while(c.size()){
int cor_nums = c.size();
Node* tmp = c.front();
c.pop_front();
if(tmp->left&&tmp->right){
c.push_back(tmp->left);
c.push_back(tmp->right);
}
for(int i=1;i<cor_nums;i++){
Node* new_node = c.front();
c.pop_front();
if(new_node->left&&new_node->right){
c.push_back(new_node->left);
c.push_back(new_node->right);
}
tmp->next = new_node;
tmp = tmp->next;
}
tmp->next=nullptr;
}
return root;
}
};