写一函数int fun(char *p)判断一字符串是否为回文，是返回1，不是返回0，出错返回-1

#include <stdio.h>int fun(char *p) {  if(p==NULL)  return -1;  else  {  int length = 0;  int i = 0;  int judge = 1; length = strlen(p); for(i=0;i <length/2; i++)  {  if(p[i]!=p[length-1-i])    judge = 0;    break;  }  if(judge == 0)  return 0;  else   return 1;  } }void main(){      char str1[]="abccba";  char str2[]="b";  int i=fun(str1);  printf("%d \n",i);}

第二种：

#include <stdio.h>int fun(char *p){ int len = strlen(p) - 1;char *q = p + len; if (!p)return -1; while (p < q) { if ((*p++) != (*q--))return 0; } return 1;}  void main(){      char str1[]="abccba";  char str2[]="b";  int i=fun(str1);  printf("%d \n",i);}