example – A = [1,0,0,0,1,1,1,0,0,0]
Output – [0,0,0,0,0,0,1,1,1,1]
- Count no. of 0s and 1s and place them that number of times in the array.
- Instead of counting number of 0s, if the current element is 0, we can place 0 at next available position (maintain a pointer) in the array. After all elements in the array are processed, we fill all remaining indices by 1.
- Partitioning approach of Quick Sort Algorithm – We can mark the pivot as 1 and each time we encounter 1 it is swapped with a 0. So in one pass our array will be sorted.