Can someone please explain me lower_bound and upper_bound and how they are used in sorted array? Please explain in depth.
# | User | Rating |
---|---|---|
1 | tourist | 3690 |
2 | jiangly | 3647 |
3 | Benq | 3581 |
4 | orzdevinwang | 3570 |
5 | Geothermal | 3569 |
5 | cnnfls_csy | 3569 |
7 | Radewoosh | 3509 |
8 | ecnerwala | 3486 |
9 | jqdai0815 | 3474 |
10 | gyh20 | 3447 |
# | User | Contrib. |
---|---|---|
1 | maomao90 | 174 |
2 | awoo | 165 |
3 | adamant | 161 |
4 | TheScrasse | 160 |
5 | nor | 158 |
6 | maroonrk | 156 |
7 | -is-this-fft- | 152 |
8 | orz | 146 |
9 | SecondThread | 145 |
9 | pajenegod | 145 |
Can someone please explain me lower_bound and upper_bound and how they are used in sorted array? Please explain in depth.
Name |
---|
int* ptr = lower_bound(a, a + n, k);
returns the pointer to the first element in
a
that is larger than or equal to kint* ptr = upper_bound(a, a + n, k);
returns the pointer to the first element in
a
that is larger than kYou can use the following to get the index. This also means "how many elements in a are smaller than k"
int index = lower_bound(a, a + n, k) - a;
Don't forget that
std::map
andstd::set
have their ownlower_bound
andupper_bound
function.According to cplusplus.com
lower_bound(a,a+n,k)
returns pointer to the first element, where k can be inserted.upper_bound(a,a+n,k)
returns pointer to the last element, where k can be inserted :).