| Topic: | Searching |
|---|---|
| Author: | Peter Bui <pbui@cse.nd.edu> |
| Date: | September 25, 2009 |
Scanning a collection is O(n), and relatively straightforward.
If we have to do multiple searches, then we can sort a container and then perform binary search for subsequent searches O(logn).
void *bsearch(const void *key, const void *base,
size_t nmemb, size_t size,
int (*compar)(const void *, const void *));
int ia[6] = { 0, 1, 2, 3, 4, 5 };
int ik;
int *ip;
qsort(ia, 6, sizeof(int), int_cmp);
ik = 4;
ip = bsearch(&ik, ia, 6, sizeof(int), int_cmp);
if (ip) printf("found %d in integer array\n", ik);
if (binary_search(iv.begin(), iv.end(), 4))
cout << "found 4 in integer vector" << endl;
vector<int>::iterator it;
it = lower_bound(iv.begin(), iv.end(), 4);
if (it != iv.end())
cout << "found 4 in integer vector" << endl;
sv.push_back(3); sv.push_back(4), sv.push_back(5);
if (includes(iv.begin(), iv.end(), sv.begin(), sv.end()))
cout << "iv contains all of sv" << endl;