Sort the three integers from large to small (introduce various methods in detail)

  Example ： Enter three integers , Show in descending order

                  Input ：4  3  5

                  Output ：5  4  3

（1） The easiest way （ Compare the two ）

  The principle is ： Mathematical ranking ( The question of shaking hands in pairs ,n Individuals have （n-1+n-2+....+1） Medium method )

#include<stdio.h>
int main()
{
	int a = 0;
	int b = 0;
	int c = 0;
	int tmp = 0;  // As a medium of exchange 
	printf(" Please enter three numbers ：\n");
	scanf("%d %d %d", &a, &b, &c);
	        if (a < b)
			{
				tmp = a;
				a = b;
				b = tmp;
			}
			if (a < c)
			{
				tmp = a;
				a = c;
				c = tmp;
			}
			if (b < c)
			{
				tmp = b;
				b = c;
				c = tmp;
			}
	printf(" Output the three numbers after sorting ：\n");
	printf("%d %d %d", a, b, c);
	return 0;
}

 （2） The method of using functions （ Principle Comparison Exchange cmp, Compare the three numbers ）

#include<stdio.h>
void cmp(int* _a, int* _b, int* _c)// The corresponding parameter in the function is the formal parameter of the main function argument , A formal parameter is a temporary copy of an argument 
{
	int tmp = 0;
	if (*_a < *_b)            //int*  Is the type of pointer variable   amount to  int  yes   Type of integer 
	{
		tmp = *_a;            //_a =&a  *_a = a  *&a=a * The function here is that the dereference operation can find the arguments 
		*_a = *_b;
		*_b = tmp;
	}
	if (*_a < *_c)
	{
		tmp = *_a;
		*_a = *_c;
		*_c = tmp;
	}
	if (*_b < *_c)
	{
		tmp = *_b;
		*_b = *_c;
		*_c = tmp;
	}
}
int main()
{
	int a = 0;
	int b = 0;
	int c = 0;
	printf(" Please enter three numbers ：\n");
	scanf("%d %d %d", &a, &b, &c);
	cmp(&a, &b, &c);
	printf(" Output the three numbers after sorting ：\n");
	printf("%d %d %d", a, b, c);
	return 0;
}

 （3） Function method （ Compare the two numbers ）

#include<stdio.h>
void cmp(int* px, int* py)  //px,py Is an address pointer that stores two numbers , It's a pointer variable , The pointer variable is the address 
{
	int z = 0;              //z For temporary storage of data , The medium of exchange 
	if (*px < *py)          //*px  Pointer operation  *px=a（a The number stored for the address ）
	{
		z = *px;
		*px = *py;
		*py = z;
	}
}
int main()
{
	int a = 0;
	int b = 0;
	int c = 0;
	printf(" Please enter three numbers ：\n");
	scanf("%d %d %d", &a, &b, &c);
	cmp(&a, &b);
	cmp(&a, &c);
	cmp(&b, &c);
	printf(" Output the three numbers after sorting ：\n");
	printf("%d %d %d", a, b, c);
	return 0;
}

（4） Use bubble sort （ Yes, but not necessarily ）

#include<stdio.h>
int main()
{
	int a[3] = { 0 };// Set the array to store three numbers , Plan to complete the order of storage from large to small 
	int i = 0;
	int j = 0;
	printf(" Please enter three numbers ：\n");
	for (i = 0; i < 3; i++) 
	{
		scanf("%d", &a[i]);
	}
	for (i = 0; i < 2; i++) //3 A digital , The first number needs to be compared with the remaining two numbers , Just do it twice 
	{
		int tmp = 0;
		for (j = 0; j < 2 - i; j++)// It has been compared before , Subtract the number of previous comparisons 
		{
			if (a[j] < a[j + 1])
			{
				tmp = a[j];
				a[j] = a[j + 1];
				a[j + 1] = tmp;
			}
		}
	}
	printf(" Output the three numbers after sorting ：\n");
	for (i = 0; i < 3; i++)
	{
		printf("%d ", a[i]);
	}
	return 0;
}