有序表中找对应值算法

int sortNumPosition (int a[],int len,int num)
{
int p = len/2;
//{1,2,4,8,16,32,64,128,256,512,1024};
// 0 1 2 3 4  5  6  7   8   9   10
for (int i = p; i > 0; i--) {
if (num > a[p]) {
p+=i/2;
}else if (num < a[p]) {
p-=i/2;
}else {
break;
}
}
printf("a[p] = %d \n",a[p]);
return p;
}

int main(int argc, const char * argv[]) {
//{1,2,4,8,16,32,64,128,256,512,1024};
// 0 1 2 3 4  5  6  7   8   9   10
int a[11] = {1,2,4,8,16,32,64,128,256,512,1024};
sortNumPosition(a,11,512);
return 0;
}