Sort Colors

sortColors.java

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

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

Note:
You are not suppose to use the library's sort function for this problem.

Algorithm:
1. There are 3 separators, red, white, and blue
2. Since the increate interator and put the correct int into 
a correct bucket by swaping them execept the white color.
*/
public class Solution {
    public void sortColors(int[] A) {
        // Start typing your Java solution below
        // DO NOT write main() function
        int red = 0;
        int white = 0;
        int blue = A.length-1;
        while(blue >= white) {
            if(A[white] == 1) {
                white++;
            } else if(A[white] == 0) {
                swap(A, white, red);
                red++;
                white++;
            } else if(A[white] == 2) {
                swap(A, white, blue);
                blue--;
            }
        }
        return;
    }
    public void swap(int[] A, int i, int j) {
        int tmp = A[i];
        A[i] = A[j];
        A[j] = tmp;
    }
}