Basic Operation string, string string copy and inverted

A: basic operating string 

Sizeof size calculation data, the array comprising '\ 0' character

strlen calculated length of the string to '\ 0' end

void test01(){
	//字符串需要有结束的标志 '\0'
	char str1[] = { 'h', 'e', 'l', 'l', 'o','\0' };
	printf("%s\n",str1);

	//字符数组部分初始化，剩余填0
	char str2[100] = {'h','e','l','l','o'};
	printf("%s\n",str2);

	//如果以字符串初始化，那么编译器默认会在字符串的尾部添加'\0'
	char str3[] = "hello";
	printf("%s\n",str3);
	printf("sizeof str3=%d\n", sizeof(str3)); //6 统计'\0'
	printf("strlen str3=%d\n",strlen(str3));  //5 不统计'\0'

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

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

	char str6[] = "hello\012world";//\012 是八进制，在十进制下在ASCII表中是换行
	printf("%s\n",str6);
	printf("sizeof str6 = %d\n", sizeof(str6));//12
	printf("strlen str5 = %d\n", strlen(str6)); //11
}

Octal and hexadecimal escape character

    There are two special characters, typically in the form of octal and hexadecimal escape character escape character, the character is octal 'in C \ ddd ', D is a number of 0-7. The general form of the hexadecimal characters ' \ xhh The ', is H or a 0-9 in the AF. Octal and hexadecimal character represents the character corresponding to the ASCII value of the character.

such as:

1. '\ 063' represents the character '3', because '3' ASCII code is 30 (hexadecimal), 48 (decimal), 63 (octal)

     2. '\ x41' represents the character 'A', since 'A' is the ASCII code 41 (hex), 65 (decimal), 101 (octal)

II: string copy function 

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
#include<string.h>


//字符串拷贝
//参数1 目标字符串 参数2 源字符串
//需求 将源字符串中的内容拷贝到目标字符串中
//第一种 利用[]进行拷贝
void copyString01(char *dest,char *source){
	int len = strlen(source);
	for (int i = 0; i < len; i++)
	{
		dest[i] = source[i];
	}
	dest[len] = '\0';
}

//第二种 利用字符串指针进行拷贝
void copyString02(char *dest ,char *source){
	while (*source != '\0'){
		*dest = *source;
		dest++;
		source++;
	}
	*dest = '\0';
}

//第三种方式
void copyString03(char *dest, char *source){
	while (*dest++ = *source++){}
}

void test02(){
	char *str = "hello world";
	char buf[1024];
	//copyString01(buf, str);
	//copyString02(buf,str);
	copyString03(buf, str);
	printf("%s\n", buf);
}

//字符串反转
//第一种方式，利用[]反转
void reverseString01(char *str){
	int len = strlen(str);
	int start = 0; //起始的位置下标
	int end = len - 1;//结束的位置下标
	while (start<end)
	{
		char temp = str[start];
		str[start] = str[end];
		str[end] = temp;
		start++;
		end--;
	}
}
//第二种方式，利用指针
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";
	//reverseString01(str);
	reverseString02(str);
	printf("%s\n",str);
}
int main(){
	test03();
	return 0;
}