As promised, here are some (nested) hints for Codeforces Round #682 (Div. 2).
1438A - Специфичные вкусы Андре
Hint 1
Hint 1
Hint 1
Hint 1
I wasn't able to solve E and F. If you did, you may want to add your hints in the comments.
# | User | Rating |
---|---|---|
1 | tourist | 4009 |
2 | jiangly | 3823 |
3 | Benq | 3738 |
4 | Radewoosh | 3633 |
5 | jqdai0815 | 3620 |
6 | orzdevinwang | 3529 |
7 | ecnerwala | 3446 |
8 | Um_nik | 3396 |
9 | ksun48 | 3390 |
10 | gamegame | 3386 |
# | User | Contrib. |
---|---|---|
1 | cry | 166 |
2 | maomao90 | 163 |
2 | Um_nik | 163 |
4 | atcoder_official | 161 |
5 | adamant | 160 |
6 | -is-this-fft- | 158 |
7 | awoo | 157 |
8 | TheScrasse | 154 |
9 | nor | 153 |
9 | Dominater069 | 153 |
Unofficial hints for Codeforces Round #682 (Div. 2) (A — D)
As promised, here are some (nested) hints for Codeforces Round #682 (Div. 2).
1438A - Специфичные вкусы Андре
Solve some small tests on paper.
Can you make the sum of each subarray equal to its length?
Suppose that the answer is NO
. Which property should hold for the array $$$a$$$?
What happens if $$$l_1 = r_1$$$?
The answer is YES
if there is a pair of equal elements in the array $$$b$$$. What happens if there are no equal elements?
Look at the binary representation of the sum of each subarray. Are there equal binary representations?
Solve on paper
3 3
1 1 1
1 1 1
1 1 1
Now solve
3 3
2 1 1
1 1 2
2 1 2
Do a chess coloring on the grid. Can you make all differences odd?
How does the xor of all the array change after every operation?
The xor remains constant. Let it be $$$x$$$. If you make all elements equal, what's the xor of the resulting array?
If $$$n$$$ is even, $$$x = 0$$$. So the answer is NO
if the starting xor is not $$$0$$$.
If $$$n$$$ is odd, you can set $$$a[i] = x$$$ for each $$$i$$$, and their xor is $$$x$$$. The answer is always YES
.
In both cases, you can solve the problem by making each $$$a[i]$$$ equal to $$$x$$$. Can you make $$$a[1] = x$$$ first?
Now you want to "spread" $$$x$$$ in all the array. Are there three indices such that $$$a[i] \oplus a[j] \oplus a[k] = x$$$?
I wasn't able to solve E and F. If you did, you may want to add your hints in the comments.
Rev. | Lang. | By | When | Δ | Comment | |
---|---|---|---|---|---|---|
en6 | TheScrasse | 2020-11-13 20:59:08 | 17 | Tiny change: '\nThe xor remains c' -> '\nThe xor of all the array remains c' | ||
en5 | TheScrasse | 2020-11-13 20:46:19 | 97 | |||
en4 | TheScrasse | 2020-11-13 20:32:22 | 34 | Tiny change: 'he array. Are ther' -> 'he array. You already have some $a[i] = x$. Are ther' | ||
en3 | TheScrasse | 2020-11-13 20:25:47 | 24 | Tiny change: 'th cases, you can ' -> 'th cases, if the answer is `YES`, you can ' | ||
en2 | TheScrasse | 2020-11-13 20:21:01 | 76 | |||
en1 | TheScrasse | 2020-11-13 20:18:34 | 2080 | Initial revision (published) |
Name |
---|