基数排序

/**
 * 基数排序
 * <ul>
 * <li>平均情况：O(d(r+n))</li>
 * <li>最好情况：O(d(rd+n))</li>
 * <li>最坏情况：O(d(r+n))</li>
 * <li>辅助存储：O(d(rd+n))</li>
 * <li>稳定</li>
 * <ul>
 * 
 * @timestamp Mar 13, 2016 8:59:32 PM
 * @author smallbug
 */
public class RadixSort {
	public static void main(String[] args) {
		int[] data = DataUtil.getData(100000);
		// System.out.println(Arrays.toString(data));
		long time = System.currentTimeMillis();
		data = radixSort(data);
		// System.out.println(Arrays.toString(data));
		System.out.println("speed " + (System.currentTimeMillis() - time) + " ms");
		System.out.println("排序是否成功：" + (DataUtil.verify(data, DataUtil.ASC) ? "是" : "否"));
	}

	private static int[] radixSort(int[] data) {
		int length = String.valueOf(data.length).toCharArray().length;
		for (int i = 1; i < length; i++) {
			int carve = (int) Math.pow(10, i);// 从个位开始比，然后十位，百位。。。
			data = bucketSort(data, carve);
		}
		return data;
	}

	private static int[] bucketSort(int[] data, int carve) {
		int[] count = new int[10];// 计数数组
		int[] result = new int[data.length];// 结果数组
		for (int i = 0; i < data.length; i++) {
			count[(data[i] % carve) / (carve / 10)]++;// 建立计数表
		}
		for (int i = 1; i < count.length; i++) {
			count[i] = count[i] + count[i - 1];// 格式化计数表
		}
		for (int i = data.length - 1; i >= 0; i--) {
			result[--count[(data[i] % carve) / (carve / 10)]] = data[i];// 根据计数表排序
		}
		return result;
	}
}