Good C++ solutions to the “Bring all the zeros to the back of the array” interview challenge

Question

I had an interview for a Jr. development job and he asked me to write a procedure that takes an array of ints and shoves the zeroes to the back. Here are the constraints (wh

Answer 1

An approach that sorts is O(N*Log₂N). There is a linear solution that goes like this:

• Set up two pointers - readPtr and writePtr, initially pointing to the beginning of the array
• Make a loop that walks readPtr up the array to the end. If *readPtr is not zero, copy to *writePtr, and advance both pointers; otherwise, advance only readPtr.
• Once readPtr is at the end of the array, walk writePtr to the end of the array, while writing zeros to the remaining elements.