Facebook Phone Interview -- Move Zeros to Right (Easy)

March 22th, 2016.

Move Zeros to the right end but keep the order of non-zero numbers.

#include <stdio.h>
#inlcude <iostream>
#include <vector>
using namespace std;

// move Zeros to the right end of the array.
// classical two pointers problem.
void moveZeroToRight(vector<int>& array) {
    if(array.size() <= 1) return; // if the array only has 0-1 values, no need to sort.
    int left = 0; // one pointer to remember the left copy.
    int i = 0; // one pointer to loop the array.
    while(i < array.size()) {
        if(array[i] != 0) {
            array[left++] = array[i++]; // if it is not zero, copy it to the left end.
        } else {
            i++;  // otherwise, i pointer keeps on moving.
        }
    }
    // copy all non-zeros to the left now. But we need to remember to set the left values to 0.
    while(left < array.size()) {
         array[left++] = 0;
    }
}

// the following is for test purpose.
void printArray(vector<int> array) {
    for(int i = 0; i < array.size(); ++i) {
         printf("%d\n", array[i]);
    }
}

int main(void) {
     vector<int> array;
     array.push_back(0); array.push_back(1);
     moveZeroToRight(array);
     printArray(array);
}