【算法导论】第八章之计数排序

asdfs

package com.zhoujie;

import java.util.Random;

/**
 * heap sort
 * @author zhoujie
 *
 */
public class CountSort {
	public static final int ARRAY_LENGTH = 10;
	public static final int ARRAY_MAX_VALUE = 100;

	public static final String LOG_PREFIX = "=====================";
	public static final String LOG_SUFFIX = LOG_PREFIX;
	public static final String ARR_DELIMITER = "\t";

	public static void main(String[] args) {
		// 1. generate input array
		Random random = new Random();

		int[] intArr = new int[ARRAY_LENGTH];
		printLine(LOG_PREFIX + "The original array is:" + LOG_SUFFIX);
		for (int i = 0; i < intArr.length; i++) {
			intArr[i] = random.nextInt(ARRAY_MAX_VALUE);
			print(intArr[i]);
			if (i != intArr.length - 1) {
				print(ARR_DELIMITER);
			}
		}
		printLine("");

		// 2. count sort
		int[] sortedArr = countSort(intArr);

		// 3. print sorted array
		printLine(LOG_PREFIX + "The sorted array is:" + LOG_SUFFIX);
		printLine(join(sortedArr, ARR_DELIMITER));
	}

	private static int[] countSort(int[] intArr) {
		int [] resultArr = new int[intArr.length];
		int [] countArr = new int[ARRAY_MAX_VALUE + 1];
		for(int i = 0; i < countArr.length; i++){
			countArr[i] = 0;
		}
		for(int item : intArr){
			countArr[item] = 1;
		}
		for(int i = 1; i < countArr.length ; i++){
			countArr[i] = countArr[i-1] + countArr[i];
		}
		for(int i = intArr.length - 1; i >= 0; i--){
			int index = countArr[intArr[i]]--;
			resultArr[index - 1] = intArr[i];
		}
		return resultArr;
	}

	public static void print(Object t) {
		System.out.print(t);
	}

	public static void printLine(Object t) {
		System.out.println(t);
	}

	public static String join(int[] arr, String delimiter) {
		StringBuilder sb = new StringBuilder();
		for (int element : arr) {
			sb.append(element);
			sb.append(delimiter);
		}
		return sb.substring(0, sb.length());
	}

}

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