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一 . 归并排序


void _MergeSort(int* arr, int left, int right, int* tmp)
{
	if (left >= right)
	{
		return;
	}
	//找中间值
	int mid = (left + right) / 2;

	//根据mid 分成两个序列:[left , mid ] [mid+1 , right]
	_MergeSort(arr, left, mid, tmp);
	_MergeSort(arr,  mid+1,right, tmp);

	//合并两个序列 [left , mid ] [mid+1 , right]
	int begin1 = left, end1 = mid;
	int begin2 = mid + 1, end2 = right;
	int index = begin1;
	while (begin1 <= end1 && begin2 <= end2)
	{
		if (arr[begin1] < arr[begin2])
		{
			tmp[index++] = arr[begin1++];
		}
		else
		{
			tmp[index++] = arr[begin2++];
		}
	}
	//可能存在第一个序列中的数据没有全部放回tmp中
	//可能存在第二个序列中的数据没有全部放回tmp中
	while (begin1 <= end1)
	{
		tmp[index++] = arr[begin1++];
	}
	while (begin2 <= end2)
	{
		tmp[index++] = arr[begin2++];
	}
	//将tmp中数据挪回arr中
	for (int i = left; i <= right; i++)
	{
		arr[i] = tmp[i];
	}
}

//归并排序
void MergeSort(int* arr, int n)
{
	int* tmp = (int*)malloc(sizeof(int) * n);
	_MergeSort(arr, 0, n - 1, tmp);
	free(tmp);
	tmp = NULL;
}

二 . 非比较排序 - 计数排序

//计数排序
void CountSort(int* arr, int n)
{
	int max = arr[0], mix = arr[0];
	//找最大、最小值
	for (int i = 0; i < n; i++)
	{
		if (max < arr[i])
		{
			max = arr[i];
		}
		if (mix > arr[i])
		{
			mix = arr[i];
		}
	}

	int range = max - mix + 1;
	//开辟数组并把它初始化为0
	int* count = (int*)calloc(range, sizeof(int));
	if (count == NULL)
	{
		perror("calloc fail!");
		exit(1);
	}

	for (int i = 0; i < n; i++)
	{
		count[arr[i] - mix]++;
	}
	int index = 0;
	for (int i = 0; i < range; i++)
	{
		while (count[i]--)
		{
			arr[index++] = i + mix;
		}
	}
}

三 . 测试代码 : 排序性能对比


// 测试排序的性能对⽐
void TestOP()
{
	srand(time(0));
	const int N = 100000;
	int* a1 = (int*)malloc(sizeof(int) * N);
	int* a2 = (int*)malloc(sizeof(int) * N);
	int* a3 = (int*)malloc(sizeof(int) * N);
	int* a4 = (int*)malloc(sizeof(int) * N);
	int* a5 = (int*)malloc(sizeof(int) * N);
	int* a6 = (int*)malloc(sizeof(int) * N);
	int* a7 = (int*)malloc(sizeof(int) * N);
	for (int i = 0; i < N; ++i)
		{
		a1[i] = rand();
		a2[i] = a1[i];
		a3[i] = a1[i];
		a4[i] = a1[i];
		a5[i] = a1[i];
		a6[i] = a1[i];
		a7[i] = a1[i];
		}
	int begin1 = clock();
	InsertSort(a1, N);
	int end1 = clock();

		int begin2 = clock();
		ShellSort(a2, N);
		int end2 = clock();
	
		int begin3 = clock();
		SelectSort(a3, N);
		int end3 = clock();

		int begin4 = clock();
		HeapSort(a4, N);
		int end4 = clock();
	
		int begin5 = clock();
		QuickSort(a5, 0, N - 1);
		int end5 = clock();

		int begin6 = clock();
		MergeSort(a6, N);
		int end6 = clock();
	
		int begin7 = clock();
		BubbleSort(a7, N);
		int end7 = clock();
	
		printf("InsertSort:%d\n", end1 - begin1);
		printf("ShellSort:%d\n", end2 - begin2);
		printf("SelectSort:%d\n", end3 - begin3);
		printf("HeapSort:%d\n", end4 - begin4);
		printf("QuickSort:%d\n", end5 - begin5);
		printf("MergeSort:%d\n", end6 - begin6);
		printf("BubbleSort:%d\n", end7 - begin7);

		free(a1);
		free(a2);
		free(a3);
		free(a4);
		free(a5);
		free(a6);
		free(a7);
	
}