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77. Construct a binary tree from given Inorder and Postorder Traversal
Objective:  Given a inorder and postorder traversal, write an algorithm to construct a binary tree from that. This problem was asked in the Microsoft coding competition.
Input: Inorder and postorder traversals
Similar Problems: Make a Binary Tree from Given Inorder and Preorder Traveral.
Appraoch:
int[] inOrder = { 4, 2, 5, 1, 6, 3, 7 };
int[] postOrder = { 4, 5, 2, 6, 7, 3, 1 };.
 Last element in the postorder [] will be the root of the tree, here it is 1.
 Now the search element 1 in inorder[], say you find it at position i, once you find it, make note of elements which are left to i (this will construct the leftsubtree) and elements which are right to i ( this will construct the rightSubtree).
 Suppose in previous step, there are X number of elements which are left of 'i' (which will construct the leftsubtree), take first X elements from the postorder[] traversal, this will be the post order traversal for elements which are left to i. similarly if there are Y number of elements which are right of 'i' (which will construct the rightsubtree), take next Y elements, after X elements from the postorder[] traversal, this will be the post order traversal for elements which are right to i
 From previous two steps construct the left and right subtree and link it to root.left and root.right respectively.
 See the picture for better explanation.
Output:
inorder traversal of constructed tree : 4 2 5 1 6 3 7