下面 search 函数的平均时间复杂度为(   )。

int search(int n, int * p, int target) {
int low = 0, high = n;
while (low <= high) {
int middle = (low + high) / 2;
if (target == p[middle]) {
return middle;
} else if (target > p[middle]) {
low = middle + 1;
} else {
high = middle - 1;
}
}
return -1;
}