leetcode 79: Populating Next Right Pointers in Each Node II

Populating Next Right Pointers in Each Node IIOct 28 '12

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. * public class TreeLinkNode { *     int val; *     TreeLinkNode left, right, next; *     TreeLinkNode(int x) { val = x; } * } */public class Solution {    public void connect(TreeLinkNode root) {        // Start typing your Java solution below        // DO NOT write main() function                if(root==null) return;                Queue<TreeLinkNode> q1 = new LinkedList<TreeLinkNode>();        Queue<TreeLinkNode> q2 = new LinkedList<TreeLinkNode>();                q1.offer( root );        root.next = null;        while( !q1.isEmpty() ) {            TreeLinkNode t = q1.poll();            if(t.left != null) q2.offer( t.left);            if(t.right!=null) q2.offer( t.right );                        t.next = q1.isEmpty() ? null : q1.peek();                        if(q1.isEmpty()) {                Queue<TreeLinkNode> temp = q1;                q1 = q2;                q2 = temp;            }        }    }}

 

/** * 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) {        // Start typing your C/C++ solution below        // DO NOT write int main() function                if(root==nullptr) return;                queue<TreeLinkNode*> que;        que.push( root);                int q1 = 1;        int q2 = 0;        while(!que.empty() ) {            TreeLinkNode * n = que.front();            que.pop();            --q1;                        if(n->left!=nullptr) {                que.push(n->left);                ++q2;            }            if(n->right!=nullptr){                que.push(n->right);                ++q2;            }                        if(q1==0) {                swap(q1,q2);            } else {                n->next = que.front();            }        }    }};