void swap(int* i1,int* i2){ 
     int temp; 
     temp = *i1; 
     *i1 = *i2; 
     *i2 = temp; 
} 

void swap(void *vp1,void *vp2){ 
    void temp = *vp1; 
    *vp1 = *vp2; 
    *vp2 = temp; 
} 

void swap(void *vp1,void *vp2,int size){ 
   char buffer[size];//注意此处gcc编译器是允许这样声明的
   memcpy(buffer,vp1,size); 
   memcpy(vp1,vp2,size); 
   memcpy(vp2,buffer,size); 
} 

int x = 27,y = 2; 
swap(&x,&y,sizeof(int)); 

int lsearch(int key,int array[],int size){
   for(int i = 0;i < size; ++i)
         if(array[i] == key)
              return i;
   return -1;
}

void* lsearch(void* key, void *base, int n, int elemSize){
  for(int i = 0;i < n; ++i){
    void *elemAddr = (char *)base+i*elemSize;
    if(memcmp(key, elemAddr, elemSize) == 0)
      return elemAddr;
  }
  return NULL;
}

void *lsearch(void *key,void *base,int n,int elemSize,int(*cmpfn)(void*,void*,int)){
  for(int i = 0;i < n; ++i){
    void *elemAddr = (char *)base+i*elemSize;
    if(cmpfn(key,elemAddr,elemSize) == 0)
      return elemAddr;
  }
  return NULL;
}

int intCmp(void* elem1,void* elem2){
    int* ip1 = elem1;
    int* ip2 = elem2;
    return *ip1-*ip2;
}

int array[] = {1,2,3,4,5,6};
int size = 6;
int number = 3;
int *found = lsearch(&number,array,size,sizeof(int),intCmp);
if(found == NULL)
     printf("NO\n");
else
     printf("YES\n");