added max width of binary tree

Author: saihariG

Trees/MaximumWidthOfBinaryTree.java

@@ -0,0 +1,65 @@
+package Trees;
+
+import java.util.LinkedList;
+import java.util.Queue;
+
+public class MaximumWidthOfBinaryTree {
+    static class TreeNode {
+        TreeNode root;
+        TreeNode left;
+        TreeNode right;
+
+        TreeNode() {}
+    }
+    public int widthOfBinaryTree(TreeNode root) {
+        if(root == null) return 0;
+        // queue to hold nodes
+        Queue<TreeNode> q = new LinkedList<>();
+        // queue to hold index of corresponding node in BFS order
+        Queue<Integer> qIndex = new LinkedList<>();
+        // adding first node
+        q.add(root);
+        // add first node's index (say 1)
+        qIndex.add(1);
+
+        int maxWidth = 0;
+        // level order traversal
+        while(!q.isEmpty()) {
+            int size = q.size();
+            // store the index of first node in a level
+            int start = 0;
+            // store the index of last node in a level
+            int end = 0;
+
+            for(int i = 0 ; i < size ; i++) {
+                // remove from both queues
+                TreeNode node = q.poll();
+                int index = qIndex.poll();
+                // if first node
+                if(i == 0) {
+                    // update start index
+                    start = index;
+                }
+                // if last node
+                if(i == size-1) {
+                    // update end index
+                    end = index;
+                }
+                // BFS logic to add left & right node to queue if present.
+                if(node.left != null) {
+                    q.add(node.left);
+                    qIndex.add(index*2);
+                }
+
+                if(node.right != null) {
+                    q.add(node.right);
+                    qIndex.add(index*2 + 1);
+                }
+            }
+            // update max width
+            maxWidth = Math.max(maxWidth , end - start + 1);
+        }
+
+        return maxWidth;
+    }
+}