int HalfSearch(int a[], int m, int n,int key)
{
int k;
int flag = 0;
if (a[m] == key)
{
return flag = m+1;
}
if (a[n] == key)
{
return flag = n+1;
}
if (key > a[n] || key < a[m])
{
return 0;
}
k = (m+n)/2;
if (a[k] == key)
{
return flag = k+1;
}
if (a[k] > key)
{
return flag = HalfSearch(a,m+1,k-1,key);
}
if (a[k] < key)
{
return flag = HalfSearch(a,k+1,n-1,key);
}
return 0;
}
int main( void )
{
int n, m;
while ( scanf("%d", &n) != EOF )
{m = HalfSearch( n );
if ( m != -1 )
printf("查找成功！元素%d位于该数组的第%d个位置.\n", n, m);
else
printf("查找失败！该数组没有元素%d.\n", n);}
return 0;
}
int main(){
int arr[LEN] = {18,15,1,2,19,20,3,12,13,14,20,15,20,4,5,6,7,16,17,10,15,8,9,10,11,20};
int i,index;
printf("array for search:\n");
for(i = 0; i < LEN; i++){
printf("%d ",arr[i]);
}
index = HalfSearch(arr,0,LEN-1,19);
printf("\nindex of 19:%d\n",index);
}
int main(void)
{
/*递归的折半查找算法*/
int flag;
int key;
int arr[10] = {2,3,5,7,8,10,12,15,19,21};
printf("请输入要查找的项：");
scanf("%d",&key);
flag = HalfSearch (arr,0,9,key);
if (flag)
{
printf("所查找的数%d位于第%d个\n",key,flag);
}
else
{
printf("没有所要查的数。\n");
}
getch();
return 0;
}
int HalfSearch(int arr[], int low, int high, int num)
{
int mid;
mid = (low+high) / 2;
if( (low>=high) && (arr[mid]!=num) ){
return -1;
}
else
{
if(arr[mid]==num){
return mid;
}
else if(arr[mid]>num){
high = mid-1;
}
else{
low = mid+1;
}
return HalfSearch(arr,low,high,num);
}
}
