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One 、 VC & Delphi , Simulation Implementation qsort：

  Two 、 Use callback letter , Simulation Implementation qsort（ By bubbling ）

3、 ... and 、 Pointer and array written test question analysis ​

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Callback function ：

1. Is a function called through a function pointer , If you put a pointer to a function ( Address ) Pass as argument to another function , When this pointer is used to call the function it points to , We call this function a callback function .
2. The callback function is not called directly by the function's implementer , But by... When a specific event or condition occurs
Called by the other party , Used to respond to the event or condition .

// Code 1：
// Bubble sort  --  It can only be used in plastic surgery 
//void bubble_sort(int* arr,int sz)
//{
//	
//	int i = 0;
//	int flag = 1;// If there is no exchange on the first trip , This indicates that the array is in the given order 
//	for (i = 0;i < sz - 1;i++)// Number of trips ,10 Elements should be 9 Trip to , The last element , There's no need to sort 
//	{
//		// Exchange per trip    The first trip is 9 Secondary exchange 
//		int j = 0;
//		for (j = 0; j< sz -1 - i ;j++)
//		{
//			if (arr[j] > arr[j+1])
//			{
//				int temp = arr[j];
//				arr[j] = arr[j + 1];
//				arr[j + 1] = temp;
//				flag = 0;
//			}
//		}
//		if (flag == 1)
//		{
//			break;
//		}
//	}
//}
//int main()
//{
//	int arr[] = {9,8,7,6,5,4,3,2,1,0};
//	int sz = sizeof(arr) / sizeof(arr[0]);
//	bubble_sort(arr,sz);
//	int i = 0;
//	for (i = 0;i < sz;i++ )
//	{
//		printf("%d ",arr[i]);
//	}
//	return 0;
//}

One 、 VC & Delphi , Simulation Implementation qsort：

#include<stdlib.h>
//qsort Can be applied to any type of comparison 
/*void qsort(void* base, size_t num, size_t size,int (*compar)(const void*, const void*));*/// Initial address , Number , The size of each element , Compare elements 


int cmp_int(const void* e1,const void* e2)
{
	return *((int*)e1) - *((int*)e2);
}

struct Stu
{
	char Name[20];
	int age;

};

int cmp_by_name(const void* e1,const void* e2)
{
	return strcmp(((struct Stu*)e1)->Name, ((struct Stu*)e2)->Name);
}


int cmp_by_age(const void* e1, const void* e2)
{
	return (((struct Stu*)e1)->age - ((struct Stu*)e2)->age);
}


void test1()
{
	int arr[] = { 9,8,7,6,5,4,3,2,1,0 };
	int sz = sizeof(arr) / sizeof(arr[0]);
	qsort(arr, sz, 4, cmp_int);
	print(arr, sz);
}

void test2()
{
	struct Stu s[3] = { {" Zhang San ",30},{" Li Si ",40},{" Wang Wu ",50} };
	int sz = sizeof(s) / sizeof(s[0]);
	int i = 0;

	/// Compare by name 
	qsort(s,sz,sizeof(s[0]),cmp_by_name);
	for (i = 0; i < 3; i++)
	{
		printf("%s\n", s[i].Name);
	}


	// Compare by age 
	qsort(s, sz, sizeof(s[0]), cmp_by_age);
	
	for (i = 0; i < 3; i++)
	{
		printf("%d\n", s[i].age);
	}
}

int main()
{
	test1();
	test2();
	return 0;
}

  Two 、 Use callback letter , Simulation Implementation qsort（ By bubbling ）

int cmp_int(const void* e1,const void* e2)
{
	return *((int*)e1) - *((int*)e2);
}


struct Stu
{
	char Name[20];
	int age;

};

int cmp_by_name(const void* e1,const void* e2)
{
	return strcmp(((struct Stu*)e1)->Name, ((struct Stu*)e2)->Name);
}

int cmp_by_age(const void* e1, const void* e2)
{
	return (((struct Stu*)e1)->age - ((struct Stu*)e2)->age);
}



void Swap(char* a,char* b,size_t width)
{
	size_t i = 0;
	for (i = 0;i < width;i++)
	{
		char temp = *a;// One byte at a time 
		*a = *b;
		*b = temp;
		a++;
		b++;
	}
}


void bubble_sort(void* base, size_t sz, size_t width, int (*cmp)(const void* e1,const void* e2))  // Define function pointers ,e1.e2 Don't write 
{
	
	 size_t  i = 0;

	for (i = 0;i < sz - 1;i++)// Number of trips ,10 Elements should be 9 Trip to , The last element , There's no need to sort 
	{
		// Exchange per trip    The first trip is 9 Secondary exchange 
		size_t j = 0;
		for (j = 0; j< sz -1 - i ;j++)
		{
			if (cmp((char*)base+ j*width,(char*)base+(j+1)*width)>0)// Because I don't know how big it is , So use the smallest char, Every skip 1 Bytes 
			{
				// In exchange for 
				Swap((char*)base + j * width, (char*)base + (j + 1) * width,width);
			}
		}
	
	}
}
void print(int* arr, int sz)
{
	int i = 0;
	for (i = 0; i < sz; i++)
	{
		printf("%d ", arr[i]);
	}
}



// Test custom Bubblesort() Sort structure 
void test2()
{
	struct Stu s[3] = { {" Zhang San ",30},{" Li Si ",40},{" Wang Wu ",50} };
	int sz = sizeof(s) / sizeof(s[0]);
	int i = 0;

	/// Compare by name 
	bubble_sort(s, sz, sizeof(s[0]), cmp_by_name);
	for (i = 0; i < 3; i++)
	{
		printf("%s\n", s[i].Name);
	}


	// Compare by age 
	bubble_sort(s, sz, sizeof(s[0]), cmp_by_age);
	for (i = 0; i < 3; i++)
	{
		printf("%d\n", s[i].age);
	}
}

 
// Test custom Bubblesort();
void test3()
{
	int arr[] = {9,8,7,6,5,4,3,2,1,0};
	int sz = sizeof(arr) / sizeof(arr[0]);
	bubble_sort(arr,sz,sizeof(arr[0]),cmp_int);
	print(arr,sz);
}


int main()
{
	test2();// Comparison of custom test structures 
	/*test3();*/// Customize bubblesort test 
	return 0;
}

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