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ConnectNextRightNodes.java
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ConnectNextRightNodes.java
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package Leetcode;
import java.util.Deque;
import java.util.LinkedList;
/**
* @author kalpak
*
* 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.
*
*/
class TreeNodeWithNext {
public int val;
public TreeNodeWithNext left;
public TreeNodeWithNext right;
public TreeNodeWithNext next;
public TreeNodeWithNext() {}
public TreeNodeWithNext(int _val) {
val = _val;
}
public TreeNodeWithNext(int _val, TreeNodeWithNext _left, TreeNodeWithNext _right, TreeNodeWithNext _next) {
val = _val;
left = _left;
right = _right;
next = _next;
}
}
public class ConnectNextRightNodes {
public static TreeNodeWithNext connect(TreeNodeWithNext root) {
Deque<TreeNodeWithNext> queue = new LinkedList<>();
if(root == null)
return root;
queue.offer(root);
while(!queue.isEmpty()) {
int len = queue.size();
for(int i = 0; i < len; i++) {
TreeNodeWithNext current = queue.poll();
if(i < len-1) // not the right leaf node
current.next = queue.peek();
if(current.left != null)
queue.offer(current.left);
if(current.right != null)
queue.offer(current.right);
}
}
return root;
}
public static TreeNodeWithNext connectRecursive(TreeNodeWithNext root) {
doConnection(root);
return root;
}
private static void doConnection(TreeNodeWithNext root) {
// base case
if(root == null || root.left == null)
return;
// At every step, connect the child nodes and recurse
// Connect the left child to the right child
root.left.next = root.right;
if(root.next != null) { // this means the current level has at least two nodes
root.right.next = root.next.left;
}
// recurse
doConnection(root.left);
doConnection(root.right);
}
public static void main(String[] args) {
TreeNodeWithNext root = new TreeNodeWithNext(12);
root.left = new TreeNodeWithNext(7);
root.right = new TreeNodeWithNext(1);
root.left.left = new TreeNodeWithNext(9);
root.left.right = new TreeNodeWithNext(2);
root.right.left = new TreeNodeWithNext(10);
root.right.right = new TreeNodeWithNext(5);
TreeNodeWithNext result = connect(root);
TreeNodeWithNext resultRecursive = connectRecursive(root);
}
}