package com.zc.manythread;
import java.util.Random;
/**
 * 歸并排序
 * @author 偶my耶
 *
 */
public class MergeSort {
    public static void mergeSort(int[] data) {
        sort(data, 0, data.length - 1);
    }
    public static void sort(int[] data, int left, int right) {
        if (left >= right)
            return;
        // 找出中間索引
        int center = (left + right) / 2;
        // 對(duì)左邊數(shù)組進(jìn)行遞歸
        sort(data, left, center);
        // 對(duì)右邊數(shù)組進(jìn)行遞歸
        sort(data, center + 1, right);
        // 合并
        merge(data, left, center, right);
        print(data);
    }
    /**
     * 將兩個(gè)數(shù)組進(jìn)行歸并，歸并前面2個(gè)數(shù)組已有序，歸并后依然有序
     *
     * @param data
     *            數(shù)組對(duì)象
     * @param left
     *            左數(shù)組的第一個(gè)元素的索引
     * @param center
     *            左數(shù)組的最后一個(gè)元素的索引，center+1是右數(shù)組第一個(gè)元素的索引
     * @param right
     *            右數(shù)組最后一個(gè)元素的索引
     */
    public static void merge(int[] data, int left, int center, int right) {
        // 臨時(shí)數(shù)組
        int[] tmpArr = new int[data.length];
        // 右數(shù)組第一個(gè)元素索引
        int mid = center + 1;
        // third 記錄臨時(shí)數(shù)組的索引
        int third = left;
        // 緩存左數(shù)組第一個(gè)元素的索引
        int tmp = left;
        while (left <= center && mid <= right) {
            // 從兩個(gè)數(shù)組中取出最小的放入臨時(shí)數(shù)組
            if (data[left] <= data[mid]) {
                tmpArr[third++] = data[left++];
            } else {
                tmpArr[third++] = data[mid++];
            }
        }
        // 剩余部分依次放入臨時(shí)數(shù)組（實(shí)際上兩個(gè)while只會(huì)執(zhí)行其中一個(gè)）
        while (mid <= right) {
            tmpArr[third++] = data[mid++];
        }
        while (left <= center) {
            tmpArr[third++] = data[left++];
        }
        // 將臨時(shí)數(shù)組中的內(nèi)容拷貝回原數(shù)組中
        // （原left-right范圍的內(nèi)容被復(fù)制回原數(shù)組）
        while (tmp <= right) {
            data[tmp] = tmpArr[tmp++];
        }
    }
    public static void print(int[] data) {
        for (int i = 0; i < data.length; i++) {
            System.out.print(data[i] + "\t");
        }
        System.out.println();
    }
    /**
     * 產(chǎn)生隨機(jī)數(shù)組
     * @param count
     * @return
     */
    private static int[]  createDate(int count) {
        int[] data=new int[count];
          Random rand = new Random();
          boolean[] bool = new boolean[100];
          int num = 0;
          for (int i = 0; i < count; i++) {
           do {
            // 如果產(chǎn)生的數(shù)相同繼續(xù)循環(huán)
            num = rand.nextInt(100);
           } while (bool[num]);
           bool[num] = true;
           data[i]=num;
          }
          return data;
    }
    public static void main(String[] args) {
        int[] data = createDate(10);
        print(data);
        mergeSort(data);
        System.out.println("排序后的數(shù)組：");
        print(data);
    }
}