Merge pull request neetcode-gh#333 from spartan218/main

[java][105] Add solution without using Array.copyOfRange()

Author: SharmaTushar1

java/105-Construct-Binary-Tree-from-Preorder-and-Inorder-Traversal.java

@@ -29,3 +29,33 @@ public TreeNode buildTree(int[] preorder, int[] inorder) {
         return root;
     }
 }
+
+// Solution without using Array copies
+class Solution {
+
+    Map<Integer, Integer> inorderPositions = new HashMap<>();
+
+    public TreeNode buildTree(int[] preorder, int[] inorder) {
+        if(preorder.length < 1 || inorder.length < 1) return null;
+
+        for(int i = 0; i < inorder.length; i ++) {
+            inorderPositions.put(inorder[i], i);
+        }
+
+        return builder(preorder, 0, 0, inorder.length-1);
+    }
+
+    public TreeNode builder(int[] preorder, int preorderIndex, int inorderLow, int inorderHigh) {
+        if (preorderIndex > preorder.length-1 || inorderLow > inorderHigh) return null;
+
+        int currentVal = preorder[preorderIndex];
+        TreeNode n = new TreeNode(currentVal);
+        int mid = inorderPositions.get(currentVal);
+
+        n.left = builder(preorder, preorderIndex+1, inorderLow, mid-1);
+        n.right = builder(preorder, preorderIndex + (mid - inorderLow) + 1, mid+1, inorderHigh);
+
+        return n;
+    }
+
+}