placement paper of national instruments

i dont remember all the questionsbut the process was like thsis for national instruments

written round
1st technical
2nd Technical
there were negative mark for wrong answers in written round

written round
    - there will be 12 - 14 questions [two question are program implimentations]
    - duration [60 mins]
    - questions type: C\C++ or algorithms
written round basically consist of small piece of code and you are supposed to find the bug in it or complete the imlimentations
Q1) multiply two numbers in a very efficent manner possible
Q2) find the order of growth of some operations
q3) find the common ancestor in a binary tree
q4) wap to check whether a binary tree is a bst or not