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){//预处理，先将右边节点 指向自己。
         if(root == NULL) return;
         root->next=root;
         preProcess(root->right);
     }
     
     void   afterProcess(TreeLinkNode *root){//后处理，先将右边节点 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");
}