#include<stdio.h>
#include<stdlib.h>
#include<malloc.h>
#include<time.h>
#include<iostream>
using namespace std;
//
void PrintArr(int *pnArr, int nlen)
{
	for (int i = 0; i < nlen; i++)
	{
		cout << pnArr[i] << endl;;
	}
	cout << endl;
}

//void Merge(int data[], int nLpos, int nRpos, int nRightEnd)
//{
//	int i;
//	int k = nLpos;
//	int nLeftEnd = nRpos;
//	int nTmpos = 0;
//	int nLen = nRightEnd - nLpos + 1;
//	//int *pnArr = (int *)malloc(sizeof(int)* nLen);
//	int *pnArr = new int[nLen];
//	++nRpos;
//
//	while (nLpos <= nLeftEnd && nRpos <= nRightEnd)
//	{
//		if (data[nLpos] <= data[nRpos])
//			pnArr[nTmpos++] = data[nLpos++];
//		else
//			pnArr[nTmpos++] = data[nRpos++];
//	}
//	while (nLpos <= nLeftEnd)
//		pnArr[nTmpos++] = data[nLpos++];
//	while (nRpos <= nRightEnd)
//		pnArr[nTmpos++] = data[nRpos++];
//
//	nTmpos = 0;
//	for (i = k; i <= nRightEnd; i++)
//		data[i] = pnArr[nTmpos++];
//
//	//free(pnArr);
//	delete pnArr;
//}
//void MergeSort(int *pnArr, int nLeft, int nRight)
//{
//	if (nLeft > nRight)
//		return;
//	if (nRight > nLeft)
//	{
//		int nMid = (nLeft + nRight) / 2;
//		MergeSort(pnArr, nLeft, nMid);
//		MergeSort(pnArr, nMid + 1, nRight);
//		Merge(pnArr, nLeft, nMid, nRight);
//	}
//}



void Merge(int arr[], int i, int j, int k)
{
    int h = i; //  這一步是易錯點 主要是記錄arr陣列剛開始排序的位置，在下面的賦值中可以用到
	int nLen = k- i + 1;
	int* tmep = new int[nLen];
	int x = 0;
	int start = i, end = k;
	int nLeftEnd = j;
    int Rbegin = j+1;
	while (start <= nLeftEnd && Rbegin <= end)
	{
		if (arr[start] <= arr[Rbegin])
			tmep[x++] = arr[start++];
		else
			tmep[x++] = arr[Rbegin++];
	}
	while (start <= nLeftEnd)
		tmep[x++] = arr[start++];
	while (Rbegin <= end)
		tmep[x++] = arr[Rbegin++];

	x = 0;
	for (int j = i; j <= end; j++)// 把排好序的陣列重新賦值給arr
		arr[j] = tmep[x++];

	delete tmep;

}
void MergeSort(int *arr, int start, int end)
{
	if (start > end)
		return;
	if (end > start)
	{
		int middle = (start + end) / 2;
		MergeSort(arr,start, middle);
		MergeSort(arr, middle+1, end);
		Merge(arr,start,middle,end);
	}
}

int main()
{
	srand(time(nullptr));
	int nArr[10];
	for (int i = 0; i < 10; i++)
		nArr[i] = rand() % 100;
	cout << "排序前：" << endl;
	PrintArr(nArr, 10);
	MergeSort(nArr, 0, 9);
	cout << "排序後" <<endl;
	PrintArr(nArr,10);
	system("pause");
	return 0;
}