| Contests - ACM Student Chapter - PSUT |
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| Private |
| Spectator |
| PSUT Programming Contest 2026 |
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| Finished |
Osama walks into a room filled with a row of glowing numbers, each one a reflection of his thoughts and memories.
The array is of length $$$n$$$, and the numbers are $$$a_1, a_2, \dots, a_n$$$, each shining with its own intensity.
He notices that each number shines with only a few glowing bits. Moreover, some pairs of numbers resonate with each other in a special way.
A pair of indices $$$(i, j)$$$ with $$$i \lt j$$$ is called beautiful if the bitwise OR of $$$a_i$$$ and $$$a_j$$$ is strictly greater than their bitwise XOR $$$\oplus$$$.
Formally, a pair $$$(i, j)$$$ is beautiful if:
$$$$$$ a_i \,|\, a_j \gt a_i \,XOR\, a_j $$$$$$
Osama wonders how many of these beautiful pairs exist in the array, each one a small moment of harmony amidst the glow.
Your task is to count all such beautiful pairs in the array.
The first line contains a single integer $$$n$$$ ($$$2 \le n \le 10^5$$$) — the length of the array.
The second line contains $$$n$$$ integers $$$a_1, a_2, \dots, a_n$$$ ($$$1 \le a_i \le 10^9$$$) — the elements of the array.
Osama guarantees that the number of set bits (ones) in the binary representation of each number $$$a_i$$$ does not exceed $$$5$$$.
Print a single integer — denotes the number of beautiful pairs asked.
33 5 6
3
57 7 7 7 7
10
In the first example:
Pair ($$$1, 2$$$): $$$3 | 5 = 7$$$, $$$3 \oplus 5 = 6$$$. Since $$$7 \gt 6$$$, this is beautiful.
Pair ($$$1, 3$$$): $$$3 | 6 = 7$$$, $$$3 \oplus 6 = 5$$$. Since $$$7 \gt 5$$$, this is beautiful.
Pair ($$$2, 3$$$): $$$5 | 6 = 7$$$, $$$5 \oplus 6 = 3$$$. Since $$$7 \gt 3$$$, this is beautiful.
All $$$3$$$ pairs are beautiful.
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