字符串拷贝

#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

void my_strcpy1(char* src, char* dest)
{
  int i = 0;
  while (src[i])
  {
    dest[i] = src[i];
    i++;
  }
  dest[i] = '\0';
}

void my_strcpy2(char* src, char* dest)
{
  while (*src)
  {
    *dest = *src;
    src++;
    dest++;
  }
  *dest = '\0';
}

int main()
{
  
  char* src = "hello";
  char* dest[100] ;
  my_strcpy2(src, dest);
  printf("%s",dest);

  return 0;
}


找字符位置

#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

char* my_strch(char* src, char* ch)
{
  while (*src)
  {
    if (*src == *ch)
    {
      return src;
    }
    src++;
  }
  return NULL;
}

int main()
{
  char* src = "hello world";
  char* ch = "o";

  
  char* ret  = my_strch(src, ch);
  if(ret != NULL)
    printf("%s", ret);


  return 0;
}


去空格

#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

void my_strnospace(char* src, char* dest)
{
  while (*src)
  {
    if (*src != ' ')
    {
      *dest = *src;
      dest++;
    }
    src++;
  }
  *dest = '\0';
}
int main()
{
  char* src = "ni chou sha";
  char dest[100];

  my_strnospace(src, dest);

  printf("%s",dest);


  return 0;
}


字串个数

#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <string.h>

int str_times(char* str, char* substr)
{
  int count = 0;
  char* p = strstr(str,substr); //"llollollo"
  while (p != NULL)
  {
    count++;
    p += strlen(substr); //3
    p = strstr(p,substr);//"llollo"
  }
  return count;
}


int main()
{
  
  char str[] = "hellollollo";
  char substr[] = "llo";

  int ret = str_times(str,substr);

  printf("%d",ret);

  return 0;
}


字符串倒序

#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <string.h>
void str_inserse(char* str)
{
  char* start = str;
  char* end = str + strlen(str) - 1;

  while (start < end)
  {
    char tmp = *start;
    *start = *end;
    *end = tmp;
    start++;
    end--;
  }
}

int main()
{
  char str[] = "helloworld"; //变量  如果拿指针创建就是常量
  
  str_inserse(str);

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


  return 0;
}


判断回文

#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <string.h>
int str_inserse(char* str)
{
  char* start = str;
  char* end = str + strlen(str) - 1;

  while (start < end)
  {
    if (*start != *end)
    {
      return 0;  //不是回文
    }
    start++;
    end--;
  }
  return 1;  //回文
}

int main()
{
  char str[] = "abccba"; //变量  如果拿指针创建就是常量

  int ret = str_inserse(str);


  if (ret == 1)
  {
    printf("回文");
  }
  else
  {
    printf("不是回文");

  }

  return 0;
}