This problem is known as the Dutch National Flag problem. Here is a Python solution using a two-pointer approach: ```python def sortColors(nums): red, white, blue = 0, 0, len(nums)-1 while white `blue`, at which point we know the array is sorted. We return the sorted array.

Question

This problem is known as the Dutch National Flag problem. Here is a Python solution using a two-pointer approach:

```python
def sortColors(nums):
    red, white, blue = 0, 0, len(nums)-1

while white <= blue:
        if nums[white] == 0:
            nums[red], nums[white] = nums[white], nums[red]
            white += 1
            red += 1
        elif nums[white] == 1:
            white += 1
        else:
            nums[white], nums[blue] = nums[blue], nums[white]
            blue -= 1
    return nums
```

Here's how it works:

1. We initialize three pointers: `red`, `white`, and `blue`. `red` is positioned at the start of the array, `white` is positioned at the start as well, and `blue` is positioned at the end of the array.

2. We start a while loop that continues until the `white` pointer is not greater than the `blue` pointer.

3. Inside the loop, we check the value at the `white` index of the array. If it's 0 (red), we swap the values at the `red` and `white` indices, then increment both `red` and `white`. This is because we know the value at `red` must have been 1 (white), as we've already moved all the 0s to the start of the array.

4. If the value at the `white` index is 1 (white), we don't need to swap anything, but we do increment `white`.

5. If the value at the `white` index is 2 (blue), we swap the values at the `white` and `blue` indices, then decrement `blue`. We don't increment `white` here, as we need to re-check the value at the `white` index on the next iteration (as it's now a new value).

6. The loop continues until `white` > `blue`, at which point we know the array is sorted. We return the sorted array.

Knowee AI · Accepted Answer