zoukankan      html  css  js  c++  java
  • Populating Next Right Pointers in Each Node I&&II ——II仍然需要认真看看

    Populating Next Right Pointers in Each Node I

    Given a binary tree

        struct TreeLinkNode {
          TreeLinkNode *left;
          TreeLinkNode *right;
          TreeLinkNode *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.

    Note:

    • You may only use constant extra space.
    • You may assume that it is a perfect binary tree (ie, all leaves are at the same level, and every parent has two children).

    For example,
    Given the following perfect binary tree,

             1
           /  
          2    3
         /   / 
        4  5  6  7
    

    After calling your function, the tree should look like:

             1 -> NULL
           /  
          2 -> 3 -> NULL
         /   / 
        4->5->6->7 -> NULL
    

    乍一看很难,理清思路后很简单的。

    /**
     * Definition for binary tree with next pointer.
     * struct TreeLinkNode {
     *  int val;
     *  TreeLinkNode *left, *right, *next;
     *  TreeLinkNode(int x) : val(x), left(NULL), right(NULL), next(NULL) {}
     * };
     */
    class Solution {
    public:
        void connect(TreeLinkNode *root) {
            if(root==NULL||root->left==NULL)
                return;
            root->left->next=root->right;
            if(root->next!=NULL)
                root->right->next=root->next->left;
            connect(root->left);
            connect(root->right);
            return ;
        }
    };

     

    II

    Follow up for problem "Populating Next Right Pointers in Each Node".

    What if the given tree could be any binary tree? Would your previous solution still work?

    Note:

    • You may only use constant extra space.

    For example,
    Given the following binary tree,

             1
           /  
          2    3
         /     
        4   5    7
    

    After calling your function, the tree should look like:

             1 -> NULL
           /  
          2 -> 3 -> NULL
         /     
        4-> 5 -> 7 -> NULL
    /**
     * Definition for binary tree with next pointer.
     * struct TreeLinkNode {
     *  int val;
     *  TreeLinkNode *left, *right, *next;
     *  TreeLinkNode(int x) : val(x), left(NULL), right(NULL), next(NULL) {}
     * };
     */
    class Solution {
    public:
           void connect(TreeLinkNode *root) {
            if(NULL == root) return;
            TreeLinkNode* start;
            TreeLinkNode* curNode;
            TreeLinkNode* nextNode;
            while(root != NULL){
                start = findStartNodeNextLev(root);
                curNode = start;
                nextNode = findNextNodeNextLev(root, start);
                while(nextNode != NULL){
                    curNode -> next = nextNode;
                    curNode = nextNode;
                    nextNode = findNextNodeNextLev(root, curNode);
                }
                root = start;
            }
        }
    private:
        TreeLinkNode* findNextNodeNextLev(TreeLinkNode* &cur, TreeLinkNode* curNextLev){
            if(cur -> left == curNextLev && cur -> right != NULL){
                return cur -> right;
            }else{
                while(cur -> next != NULL){
                    cur = cur -> next;
                    if(cur -> left != NULL && cur -> left != curNextLev) return cur -> left;
                    if(cur -> right != NULL && cur -> right != curNextLev) return cur -> right;
                }
            }
            return NULL;
        }
        
        TreeLinkNode* findStartNodeNextLev(TreeLinkNode* node){
            if(NULL == node) return NULL;
            if(node -> left != NULL) return node -> left;
            return findNextNodeNextLev(node, node -> left);
        }
    };

      

  • 相关阅读:
    弹出框背景色透明滚动条滚动仍然居中
    日常css和js小知识点记录
    手机端上传未知图片大小,js设置宽高比例
    IE6兼容透明背景图
    css考核点整理(七)-css sprites技术的使用心得
    css考核点整理(六)-水平居中定位的几种方式
    css考核点整理(五)-css3新增的常用属性
    css考核点整理(四)-css盒模型
    css考核点整理(三)-css选择器的使用
    css考核点整理(二)-css层叠机制
  • 原文地址:https://www.cnblogs.com/qiaozhoulin/p/4746862.html
Copyright © 2011-2022 走看看