1,1,1,2,0. Assume right now p1 is pointing at 2 but p1 is at the first 1. If we just swap 0 and the first 1, it’s not correct (0,1,1,2,1). We need anotehr step to swap(p1, nums[i]) - (0,1,1,1,2).

Question:

Given an array nums with n objects colored red, white, or blue, sort them in-place so that objects of the same color are adjacent, with the colors in the order red, white, and blue.

We will use the integers 0, 1, and 2 to represent the color red, white, and blue, respectively.

You must solve this problem without using the library’s sort function.