https://www.spoj.com/problems/DQUERY/
can anybody give me a fenwick tree approach for this problem?
Thanks.
№ | Пользователь | Рейтинг |
---|---|---|
1 | tourist | 4009 |
2 | jiangly | 3773 |
3 | Radewoosh | 3646 |
4 | ecnerwala | 3624 |
5 | jqdai0815 | 3620 |
5 | Benq | 3620 |
7 | orzdevinwang | 3612 |
8 | Geothermal | 3569 |
8 | cnnfls_csy | 3569 |
10 | Um_nik | 3396 |
Страны | Города | Организации | Всё → |
№ | Пользователь | Вклад |
---|---|---|
1 | Um_nik | 163 |
2 | cry | 161 |
3 | maomao90 | 160 |
4 | -is-this-fft- | 159 |
5 | awoo | 158 |
6 | atcoder_official | 157 |
7 | adamant | 155 |
8 | nor | 154 |
9 | maroonrk | 152 |
10 | Dominater069 | 148 |
https://www.spoj.com/problems/DQUERY/
can anybody give me a fenwick tree approach for this problem?
Thanks.
Название |
---|
Sort all queries by j, create an array L initially consisting of N zeros, then for each
ind = 0...N-1
setL[ind] = 1
andL[pos] = 0
, where pos is the previous occurrence ofa[ind]
ina
, now you can answer on all queries[i, ind]
by finding sum ofL[i...ind]
.can you explain more? I don't get your approach.
What exactly?
L[i] = 1
means thati
is the last occurrence ofa[i]
in the current prefix.thanks a lot! I finally got it.