C语言代码（指针）20240306

C语言代码（指针）20240306

#define _CRT_SECURE_NO_WARNINGS
#define NDEBUG
#include <stdio.h>
#include <string.h>
#include <assert.h>

void Func(int arr[],int len)
{
	int i = 0;
	int j = len - 1;
	while (i < j)
	{
		while (i < j && arr[i] % 2 != 0)
		{
			证明是奇数
			i++;
		}
		i下标就是偶数了 
		while (i < j && arr[j] % 2 == 0)
		{
			证明是偶数
			j--;
		}
		j下标就是奇数了 

		int tmp = arr[i];
		arr[i] = arr[j];
		arr[j] = tmp;
	}
}
void Show(int arr[], int len)
{
	for (int i = 0; i < len; i++)
	{
		printf("%d ", arr[i]);
	}
	printf("\n");
}
int main()
{
	int arr[] = { 1,2,3,4,5,6,7,8,9 };
	int len = sizeof(arr) / sizeof(arr[0]);
	Func(arr, len);
	Show(arr, len);
	return 0;
}


#if 0
int MyStrlen(char* str)
{
	assert(str != NULL);
	if (str == NULL)
	{
		printf("%s\n","NULL");
		return;
	}
	int count = 0;
	char* p = str;
	while (*p != '\0')
	{
		count++;
		p++;
	}
	return count;
}
int main()
{

	char* str = "abcdef";
	int len = MyStrlen(str);
	printf("%d\n", len);

	return 0;
}

int main()
{
	
	int arr[10] = { 1,2,3,4,5,6,7,8,9,10};
	int* p = arr;
	for (int i = 0; i < 9; i++)
	{
		printf("%d ", *(p + i));
	}

	return 0;
}

int main()
{
	int* p = NULL;
	int arr[10] = { 0 };
	p = arr;
	int (*p2)[10] = &arr;//整个数组的地址 -》 指针接收这个地址-》存 整个数组 地址的指针 
	- > 指向数组的指针 
	return 0;
}




void Func1(char src[],int k)
{
	int len = strlen(src);
	求得真实的移动次数
	int time = k % len;
	for (int i = 0; i < time; i++)
	{
		每次移动一个
		char tmp = src[0];
		int j = 0;
		for (; j < len-1; j++)
		{
			移动数据
			src[j] = src[j + 1];
		}
		src[j] = tmp;
		B  C  D  A
	}
}
void Func2(char src[], int k)
{
	会使用到 库函数
	strcpy() 字符串拷贝
	strncat()
	int len = strlen(src);
	求得真实的移动次数
	int time = k % len;
	char tmp[256] = { 0 };
	从src + time的位置 开始拷贝字符串到tmp里面 
	strcpy(tmp, src + time);
	把src开始的元素 拷贝到tmp这个字符串的后面，拷贝time个
	strncat(tmp,src,time);
	strcpy(src, tmp);
}
void Reverse(char str[], int i, int j)
{
	while (i < j)
	{
		char tmp = str[i];
		str[i] = str[j];
		str[j] = tmp;
		i++;
		j--;
	}
}
void Func(char src[], int k)
{
	int len = strlen(src);
	int time = k % len;
	Reverse(src, 0, time - 1);
	Reverse(src, time, len - 1); 
	Reverse(src, 0, len - 1);
}
int main()
{
	char str[] = "abcd";
	Func(str, 3);
	printf("%s\n", str);/**/


	char str[] = "abcd";
	Func(str, 4);
	char str2[100] = { 0 };
	strcpy(str2,str);//把str第一个字符开始的数据 拷贝到str2中

	char str[] = "abcd";
	char str2[10] = "pool";
	strcat(str2,str);//在str2的后边 拼接 str
	strncat(str2,str,2);//在str2的后边 拼接 str当中的n个字符
	printf("%s\n", str2);
}

void Reverse(char str[])
{
	int len = strlen(str);
	char* left = str;
	char* right = str + len - 1;
	while (left < right)
	{
		char tmp = *left;
		*left = *right;
		*right = tmp;
		left++;
		right--;
	}
}

int main()
{
	char str[10000] = {0};
	scanf("%s",str);
	gets(str);
	char str[] = "abcdef";
	char *str = "abcdef";
	Reverse(str);
	printf("%s\n", str);
	return 0;
}

int main()
{
	unsigned long pulArray[] = { 6,7,8,9,10 };
	unsigned long* pulPtr;
	pulPtr = pulArray;
	*(pulPtr + 3) += 3;
	*(pulPtr + 3) = *(pulPtr + 3)+ 3;
	printf("%d,%d\n", *pulPtr, *(pulPtr + 3));


	char ch = 'a';
	const char* p = &ch;
	char ch2 = 'b';
	p = &ch2;
	*p = 'p';


}
int main6()
{
	int arr[] = { 1,2,3,4,5 };
	short* p = (short*)arr;
	int i = 0;
	for (i = 0; i < 4; i++)
	{
		*(p + i) = 0;
	}

	for (i = 0; i < 5; i++)
	{
		printf("%d ", arr[i]);
	}
	return 0;
}
int Func(int arr[],int len)
{
	int ret = 0;
	for (int i = 0; i < len; i++)
	{
		ret ^= arr[i];
	}
	return ret;
}
int main5()
{
	int arr[] = { 1,2,3,4,5,4,3,2,1 };
	int ret = Func(arr,sizeof(arr)/sizeof(arr[0]));
	printf("%d\n", ret);
	return 0;
}
int i;
int main4()
{
	i--;
	if (i > sizeof(i))
	{
		printf(">\n");
	}
	else
	{
		printf("<\n");
	}
	return 0;
}
int main3()
{
	int n = 2;
	int m = 5;
	int ret = n ^ m;
	int count = 0;
	求ret中二进制1的个数
	while (ret != 0)
	{
		ret = ret & (ret - 1);
		count++;
	}
	printf("%d\n", count);
	
	return 0;
}
int main2()
{
	int n = 7;
	for (int i = 30; i >= 0; i -= 2)
	{
		printf("%d ", ((n >> i) | 0));
	}
	printf("\n");
	for (int i = 31; i >= 1; i -= 2)
	{
		printf("%d ", ((n >> i) | 0));
	}
	return 0;
}
int main1()
{
	int n = 7;
	for (int i = 30; i >= 0; i -= 2) 
	{
		printf("%d ",((n >> i) & 1));
	}
	printf("\n");
	for (int i = 31; i >= 1; i -= 2)
	{
		printf("%d ", ((n >> i) & 1));
	}
	return 0;
}
#endif