swap1.java

/**
 * Created by Kareem on 12/18/16.
 */

public class swap1 {

    public static void main (String[] args) {
        int arr[] = {1, 9, 8, 4, 0, 0, 2, 7, 0, 6, 0, 9};

        swapZeros(arr);

        for(int i = 0; i < arr.length; i++){
            System.out.print(arr[i]);
        }
    }

    public static void swapZeros(int[] nums){

        int count = 0;  // Count of non-zero elements

        // Traverse the array. If element encountered is
        // non-zero, then replace the element at index 'count'
        // with this element
        for (int i = 0; i < nums.length; i++)
            if (nums[i] != 0)
                nums[count++] = nums[i]; // here count is incremented

        // Now all non-zero elements have been shifted to
        // front and 'count' is set as index of first 0.
        // Make all elements 0 from count to end.
         while (count < nums.length)
          nums[count++] = 0;
        
    }
}