Populating Next Right Pointers in Each Node

116. Populating Next Right Pointers in Each Node

  

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

#include <iostream>
#include <vector>
#include <string>
#include <sstream> 
#include <stack> 
#include <iostream>
#include <algorithm>
#include <math.h>
#include <limits.h>
using namespace std;

struct TreeLinkNode {
	int val;
	TreeLinkNode *left;
	TreeLinkNode *right;
	TreeLinkNode *next;
	TreeLinkNode(int val){
		this->val=val;
		this->left = this->right=this->next = NULL;
	}
};

void process(TreeLinkNode *cur,TreeLinkNode *nextNode){
	if(cur==NULL) {
		return;
	}
	if(nextNode==NULL) {
		cur->next=NULL;
		return;
	}
	cur->next=nextNode;

	process(cur->left,cur->right);  
	process(cur->right,cur->next->left);  
}

     void   preProcess(TreeLinkNode *root){//預處理，先將右邊節點 指向自己。
         if(root == NULL) return;
         root->next=root;
         preProcess(root->right);
     }
     
     void   afterProcess(TreeLinkNode *root){//後處理，先將右邊節點 指向NULL。
         if(root == NULL) return;
          root->next=NULL;
         afterProcess(root->right);
     }

void connect(TreeLinkNode *root) {
	if(root == NULL) return;
	preProcess(root);
	process(root->left,root->right);  
	process(root->right,root->next->left);  
	afterProcess(root);


}

int  main(){
	TreeLinkNode* root=new TreeLinkNode(0);//test1
	root->left=new TreeLinkNode(1);
	root->right=new TreeLinkNode(2);

	root->left->left=new TreeLinkNode(3);
	root->left->right=new TreeLinkNode(4);

	root->right->left=new TreeLinkNode(5);
	root->right->right=new TreeLinkNode(6);
	
	connect(root);
	cout<< "maxPathSum(root)="<<endl;
	system("pause");
}