String intensive training - copy string | string inversion implementation

1. A string has an end flag \0
2. There are three ways to copy strings
   1. utilize []
   2. Use the pointer
   3. utilize while (*dest++ = *source++){}
3. There are two ways to reverse a string
   1. utilize []
   2. Use the pointer

String basic operation

 

void test01()
{

	// Note that the string needs to have an end sign  '\0'
	char str1[] = { 'h', 'e', 'l', 'l', 'o','\0' };
	printf("str1:%s\n", str1);
}

 

void test01(){
    // Character array part initialization , Residual filling 0
	char str2[100] = { 'h', 'e', 'l', 'l', 'o' };
	printf("str2:%s\n", str2);
}

 

void test01(){
    // If initialized as a string , Then the compiler will add... At the end of the string by default '\0'
	char str3[] = "hello";
	printf("str3:%s\n", str3);
	printf("sizeof str3:%d\n", sizeof(str3)); // Statistics  \0
	printf("strlen str3:%d\n", strlen(str3)); // No statistics  \0
}

 

void test01(){
    char str4[100] = "hello";
	printf("sizeof str4:%d\n", sizeof(str4)); // 100
	printf("strlen str4:%d\n", strlen(str4)); // 5
}

 

void test01(){
    char str5[] = "hello\0world";
	printf("str5:%s\n", str5);
	printf("sizeof str5:%d\n", sizeof(str5)); //12
	printf("strlen str5:%d\n", strlen(str5)); //5
}

 

void test01(){
    char str6[] = "hello\012world";  // \012  It's octal.   Down decimal 10, stay ASCII In the table is a newline 
	printf("str6: %s\n", str6);
	printf("sizeof str6:%d\n", sizeof(str6)); // 12   
	printf("strlen str6:%d\n", strlen(str6)); // 11 
}

   String copy function implementation

 

//  Parameters 1   Target string    Parameters 2   The source string    
//  demand    The contents of the source string    Copy to target string 
//  The first one is    utilize [] The way   Copy 
void copyString01(char * dest, char * source)
{
	int len = strlen(source);
	for (int i = 0; i < len; i++)
	{
		dest[i] = source[i];
	}

	dest[len] = '\0';

}

void test02()
{
	char * str = "hello world";

	char buf[1024];

	copyString01(buf, str);

	printf("%s\n", buf);
}

// The second kind   Copy with string pointer 
void copyString02(char * dest, char * source)
{


	while (*source != '\0')
	{
		*dest = *source;
		dest++;
		source++;
	}

	*dest = '\0';
}

void test02()
{
	char * str = "hello world";

	char buf[1024];

	copyString02(buf, str);

	printf("%s\n", buf);
}

// The third way  
void copyString03(char * dest, char * source)
{
	while (*dest++ = *source++) {}

	/*int a = 0;
	while (a = 0)
	{
	printf("a");
	}*/
}

void test02()
{
	char * str = "hello world";

	char buf[1024];

	copyString03(buf, str);

	printf("%s\n", buf);
}

String inversion model

  The first way utilize [] Reverse

void reverseString01(char * str)
{
	int len = strlen(str);

	// Start position subscript 
	int start = 0;

	// Subscript of end position 
	int end = len - 1;

	while (start < end)
	{
		char temp = str[start];
		str[start] = str[end];
		str[end] = temp;

		start++;
		end--;
	}
}

void test03()
{
	char str[] = "abcdefg";
	reverseString01(str);
	
	printf("%s\n", str);
}

  The second way   Use the pointer

void reverseString02(char * str)
{
	int len = strlen(str);

	char * start = str;

	char * end = str + len - 1;

	while (start < end)
	{
		char temp = *start;
		*start = *end;
		*end = temp;

		start++;
		end--;
	}
}

void test03()
{
	char str[] = "abcdefg";

	reverseString02(str);
	printf("%s\n", str);
}