CodingProblems/FlattenBinaryTree.java at master · PerrySong/CodingProblems · GitHub

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importjava.util.LinkedList;
importjava.util.Queue;
importjava.util.Stack;

publicclassFlattenBinaryTree {
publicstaticvoidflatten(TreeNoderoot) {
if(root == null || root.left == null && root.right == null) return;
Stack<TreeNode> stack = newStack<TreeNode>();
Queue<TreeNode> queue = newLinkedList<TreeNode>();
stack.push(root);
queue.offer(root);
TreeNodetmp = root;
while(!stack.isEmpty()) {

if(tmp != null && tmp.left != null) {
tmp = tmp.left;
stack.push(tmp);
queue.offer(tmp);
 } elseif(tmp != null && tmp.right != null){
tmp = tmp.right;
stack.push(tmp);
queue.offer(tmp);
 } else {
tmp = stack.pop().right;
 }
 }


TreeNodeprev = queue.poll();
tmp = queue.poll();
while(!queue.isEmpty()) {
prev.right = tmp;
prev.left = null;
prev = tmp;
tmp = queue.poll();

 }
prev.left = null;
prev.right = tmp;
 }

publicstaticvoidmain(String[] args) {
TreeNodea = newTreeNode(1);
TreeNodeb = newTreeNode(2);
TreeNodec = newTreeNode(3);
TreeNoded = newTreeNode(4);
TreeNodee = newTreeNode(5);
TreeNodef = newTreeNode(6);
a.left = b;
a.right = e;
b.left = c;
b.right = d;
e.right = f;
flatten(a);
while(a != null) {
System.out.println(a.val);
a = a.right;
 }
 }
}