sorting an array using 0(n) code example

Example 1: sort an array of 0s 1s and 2s

Approach: Count the number of 0s, 1s and 2s in the given array. 
Then store all the 0s in the beginning followed by all the 1s then
all the 2s.
Algorithm:
1)Keep three counter c0 to count 0s, c1 to count 1s and c2 to count 2s
2)Traverse through the array and increase the count of c0 is the 
  element is 0,increase the count of c1 if the element is 1 and 
  increase the count of c2 if the element is 2
3)Now again traverse the array and replace first c0 elements with 0, 
  next c1 elements with 1 and next c2 elements with 2.

//GfG PseudoCode

Example 2: Sort an array of 0’s, 1’s and 2’s

# Utility function to swap elements `A[i]` and `A[j]` in the list
def swap(A, i, j):
 
    temp = A[i]
    A[i] = A[j]
    A[j] = temp
 
 
# Linear time partition routine to sort a list containing 0, 1, and 2.
# It is similar to 3–way partitioning for the Dutch national flag problem.
def threeWayPartition(A, end):
 
    start = mid = 0
    pivot = 1
 
    while mid <= end:
        if A[mid] < pivot:    # current element is 0
            swap(A, start, mid)
            start = start + 1
            mid = mid + 1
        elif A[mid] > pivot: # current element is 2
            swap(A, mid, end)
            end = end - 1
        else:                # current element is 1
            mid = mid + 1