以下代码的最坏时间复杂度为什么是O(N)?
/*
* V is sorted
* V.size() = N
* The function is initially called as searchNumOccurrence(V, k, 0, N-1)
*/
int searchNumOccurrence(vector<int> &V, int k, int start, int end) {
if (start > end) return 0;
int mid = (start + end) / 2;
if (V[mid] < k) return searchNumOccurrence(V, k, mid + 1, end);
if (V[mid] > k) return searchNumOccurrence(V, k, start, mid - 1);
return searchNumOccurrence(V, k, start, mid - 1) + 1 + searchNumOccurrence(V, k, mid + 1, end);
}