回呼函數應用之比較兩個對象大小

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

typedef int (*cmp)(void const* one,void const* other); //抽象函數,比較兩個對象大小

int cmp_int(void const *one,void const *other) //具體函數比較兩個整數大小
{
 const int *a=(int*)one; //必須轉化
 const int *b=(int*)other;
 if(*a>*b) return 1;
 else if(*a==*b) return 0;
 else return -1;
}

int cmp_string(void const *one,void const *other) //具體函數比較兩個字串大小
{
 const char *str1=(char*)one;
 const char *str2=(char*)other;
 return strcmp(str1,str2);
}

void const *MaxofTwo(void const *one,void const *other,cmp func) //回呼函數,返回兩個對象最大的那個
{
 if(func(one,other)>=0) return one;
 else return other;
}

void InputException()
{
 printf("Input Exception!\n");
 exit(0);
}

void MemException()
{
 printf("Memeory Exception!\n");
 exit(0);
}

void inputstring(char *&s,int len) //輸入字串,防止緩衝區溢位,len是最多可輸入字元數
{
 int i;
 if(len<=0) InputException();
 s=(char*)malloc(sizeof(len));
 if(!s) MemException();
 char *p;
 char c;
 i=0;
 p=s;
 while((c=getchar())!='\n' && i++<len)
 {
  *p++=c;
 }
 if(i<=len) s[i]='\0';
 else s[i-1]='\0';
 fflush(stdin);
}

int main(int argc,char **argv)
{
 int a,b;
 printf("a=");
 if(scanf("%d",&a)<=0) InputException();
 printf("b=");
 if(scanf("%d",&b)<=0) InputException();
 int *c=(int*)MaxofTwo(&a,&b,cmp_int); //必須轉化
 printf("The max Value betwwen %d and %d is %d\n",a,b,*c);
 getchar(); //接收斷行符號
 char *s1,*s2;
 printf("The first string is:");
 inputstring(s1,30);
 printf("The second string is:");
 inputstring(s2,30);
 char *str=(char*)MaxofTwo(s1,s2,cmp_string);
 printf("The Max string is:");
 puts(str);
 return 0;

}