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July10_2020.java
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July10_2020.java
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// Flatten the double link list - traverse next until node has child.
class Solution {
public Node flatten(Node head) {
Stack<Node> stack = new Stack<>();
Node node = head, next = null;
while(node != null){
if(node.child != null){
// setting next to stack
if(node.next != null){
next = node.next;
next.prev = null;
stack.push(next);
}
// setting child to list
node.next = node.child;
node.next.prev = node;
node.child = null;
}
if(node.next == null && stack.size() > 0){
next = stack.pop();
node.next = next;
next.prev = node;
}
node = node.next;
}
return head;
}
}