add inorder traversal using stack

Author: akgmage

Trees/Binary Trees/inorder_traversal.java

@@ -0,0 +1,37 @@
+
+/**
+ * Given the root of a binary tree, return the inorder traversal of its nodes' values.
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+/**
+ 
+ */
+class Solution {
+    public List<Integer> inorderTraversal(TreeNode root) {
+        List<Integer> li = new ArrayList<>();
+        Stack<TreeNode> s = new Stack<>();
+        TreeNode curr = root;
+        while(curr != null || !s.isEmpty()) {
+            while(curr != null) {
+                s.push(curr);
+                curr = curr.left;
+            }
+            curr = s.pop();
+            li.add(curr.val);
+            curr = curr.right;
+        }
+    return li;
+    }
+}