It would be level order and inorder.
To construct a binary tree uniquely inorder is a must along with it either postorder or preorder or level order can be there.
for eg let us take two trees:
Tree1:
root=a;
root->left=b;
root->left->right=c;
Tree2 :
root=a;
root->right=b;
root->right->left=c;
Both the trees have same preorder , postorder and levelorder So they cant be created with the help of this.LEVEL ORDER: a b c
pre-order - a b c
post-order - c b a
Preorder, as its name, always visits root first and then left and right sub-trees. That is to say, walking through a pre-order list, each node we hit would be a "root" of a sub-tree.
Post-order, as its name, always visits left and right sub-trees first and then the root. That is to say, walking through a post-order list backward, each node we hit would be a "root" of a sub-tree.
Level oder visits the tree level by level.
In-order, on the other hand, always visits left sub-tree first and then root and then right sub-tree, which means that given a root(which we can obtain from the pre-order or post-order traversal as stated above), in-order traversal tells us the sizes of the left and right sub-trees of a given root and thus we can construct the original tree.(This is the reason why inorder is needed)
Same is the case with level-order traversal. Thus if we want to obtain a unique tree we need an in-order traversal along with any other of the three traversals.
