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IterativeSolution.java
37 lines (33 loc) · 1 KB
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IterativeSolution.java
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package binarytreepostordertraversal;
import datastructures.TreeNode;
import java.util.ArrayDeque;
import java.util.LinkedList;
import java.util.List;
class IterativeSolution {
List<Integer> postorderTraversal(TreeNode root) {
ArrayDeque<TreeNode> nodes = new ArrayDeque<>();
LinkedList<Integer> traversal = new LinkedList<>();
// empty root
if(root == null)
return traversal;
// add root
nodes.add(root);
TreeNode left, right, curr;
while(!nodes.isEmpty()) {
// fetch last element in list
curr = nodes.pollLast();
// add it to first position in traversal
traversal.addFirst(curr.val);
left = curr.left;
right = curr.right;
// add left and right children
if(left != null) {
nodes.add(left);
}
if(right != null) {
nodes.add(right);
}
}
return traversal;
}
}