1.1 Sort Colors 单词遍历给0，1，2排序 leetcode

本文介绍了一种不使用库排序函数的颜色排序算法。该算法通过遍历数组中的0、1、2并将其按顺序排列来实现红、白、蓝三色排序。文章提供了一个一程算法示例，使用常数空间完成排序。

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1.1 Sort Colors 单词遍历给0，1，2排序

Given an array with n objectscolored red, white or blue, sort them so that objects of the same color areadjacent, with the colors in the order red, white and blue.

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

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

Follow up: A rather straight forwardsolution is a two-pass algorithm using counting sort. First, iterate the arraycounting number of 0's, 1's, and 2's, then overwrite array with total number of0's, then 1's and followed by 2's.

Could you come up with an one-pass algorithmusing only constant space?

package Array;

import java.util.Arrays;

/**
 * @Title: SortColors.java
 * @Package Array
 * @Description: TODO
 * @author nutc
 * @date 2013-9-6 下午2:39:08
 * @version V1.0
 */
public class SortColors {

	public static void main(String args[]) {
		SortColors s = new SortColors();

		int[] a = { 2,0};
		s.sortColors(a);
		System.out.println(Arrays.toString(a));
	}

	public void sortColors(int[] A) {
		if (A == null)
			return;

		int i = 0, j = A.length - 1, k = 0;

		 while (i < A.length && A[i] == 0)
		 i++;
		 while (j >= 0 && A[j] == 2)
		 j--;
		k = i;
		while (k <= j && i <= j) {

			if (A[k] == 0) {
				if (k > i) {
					int temp = A[i];
					A[i] = A[k];
					A[k] = temp;
					i++;
				}else{
					k++;
				}
			} else if (A[k] == 2) {
				int temp = A[j];
				A[j] = A[k];
				A[k] = temp;
				j--;
			} else {
				k++;
			}
		}

	}

}