sortColors.java

package week5;

/***
 * 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.
 *
 *
 *
 * Example 1:
 *
 * Input: nums = [2,0,2,1,1,0]
 * Output: [0,0,1,1,2,2]
 * Example 2:
 *
 * Input: nums = [2,0,1]
 * Output: [0,1,2]
 *
 */
public class sortColors {

    public void sortColors(int[] nums) {
        int c0, c1, c2, n = nums.length;
        c0 = c1 = c2 = 0;

        for (int i = 0; i < n; i++) {
            if (nums[i] == 0) c0++;
            else if (nums[i] == 1) c1++;
            else if (nums[i] == 2) c2++;
        }
        int index = 0;

        for (int i = 0; i < c0; i++) {
            nums[index++] = 0;
        }
        for (int i = 0; i < c1; i++) {
            nums[index++] = 1;
        }
        for (int i = 0; i < c2; i++) {
            nums[index++] = 2;
        }

    }

}