Programming Praxis

We have three simple interview questions today:

1) Verify that a binary tree is a binary search tree. In a binary search tree, all nodes to the left of the current node have values less than the value of the current node, all nodes to the right of the current node have values greater than the value of the current node, and those two rules hold for all nodes in the tree.

2) Remove duplicates from a list.

3) A girl counts on her fingers by counting 1 on her thumb, 2 on her index finger, 3 on her middle finge, 4 on her ring finger, and 5 on her pinkie. Then she continues the other way, counting 6 on her ring finger, 7 on her middle finger, 8 on her index finger, and 9 on her thumb. Then she continues the other other way, counting 10 on her index finger, 11 on her middle finger, 12 on her ring finger, and 13 on her pinkie. She continues in this way indefinitely. Write a program that, given n, determines which finger she will be on when her count reaches n.

Your task is to write programs that solve the three interview questions given above. When you are finished, you are welcome to read or run a suggested solution, or to post your own solution or discuss the exercise in the comments below.

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