字符串逆序（多种解法）

1:>

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include <string.h>
void reverse_string(char arr[])
{
  int l = 0;
  int r = strlen(arr) - 1;
  while (l < r)
  {
    char tmp = arr[l];
    arr[l] = arr[r];
    arr[r] = tmp;
    l++;
    r--;
  }
  }
int main()
{
  char arr[] = { "abcdef" };
  reverse_string(arr);//arr是数组名，数组名是首元素的地址
  printf("%s\n", arr);//fedcba
  return 0;
}

2:>

#include <stdio.h>
#include <string.h>
void reverse_string(char*str)
{
  int l = 0;
  int r = strlen(str) - 1;
  while (l < r)
  {
    char tmp = *(str + l);
    *(str + l) = *(str + r);
    *(str + r) = tmp;
    l++;
    r--;
  }
}
int main()
{
  char arr[] = { "abcdef" };
  reverse_string(arr);
  printf("%s",arr);
  return 0;
}

3:>

#include <stdio.h>
int Strlen(char* str)
{
  int count = 0;
  while (*str != '\0')
  {
    count++;
    str++;
  }
  return count;
}
void reverse_string(char*str)
{
  int l = 0;
  int r = Strlen(str) - 1;
  while (l < r)
  {
    char tmp = *(str + l);
    *(str + l) = *(str + r);
    *(str + r) = tmp;
    l++;
    r--;
  }
}
int main()
{
  char arr[] = { "abcdef" };
  reverse_string(arr);
  printf("%s",arr);
  return 0;
}

4:>

#include <stdio.h>
int Strlen(char* str)
{
  int count = 0;
  while (*str != '\0')
  {
    count++;
    str++;
  }
  return count;
}
void reverse_string(char* str)
{
  int len = Strlen(str);
  char tmp = *str;
  *str = *(str + len - 1);
  *(str + len - 1) = '\0';
  if (Strlen(str + 1) >= 2)
    reverse_string(str + 1);
  *(str + len - 1) = tmp;
}
int main()
{
  char arr[] = { "abcdef" };
  reverse_string(arr);
  printf("%s", arr);
  return 0;
}