Tasks Details
medium
1.
CountDiv
Compute number of integers divisible by k in range [a..b].
Task Score
100%
Correctness
100%
Performance
100%
Write a function:
def solution(a, b, k)
that, given three integers A, B and K, returns the number of integers within the range [A..B] that are divisible by K, i.e.:
{ i : A ≤ i ≤ B, i mod K = 0 }
For example, for A = 6, B = 11 and K = 2, your function should return 3, because there are three numbers divisible by 2 within the range [6..11], namely 6, 8 and 10.
Write an efficient algorithm for the following assumptions:
- A and B are integers within the range [0..2,000,000,000];
- K is an integer within the range [1..2,000,000,000];
- A ≤ B.
Copyright 2009–2025 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
Solution
Programming language used Ruby
Time spent on task 14 minutes
Notes
not defined yet
Code: 17:15:10 UTC,
rb,
verify,
result: Passed
Analysis
Code: 17:16:04 UTC,
rb,
verify,
result: Failed
Analysis
expand all
Example tests
1.
0.097 s
WRONG ANSWER,
got 2 expected 3
Code: 17:17:47 UTC,
rb,
verify,
result: Failed
Analysis
expand all
Example tests
1.
0.098 s
WRONG ANSWER,
got 2 expected 3
Code: 17:18:02 UTC,
rb,
verify,
result: Passed
Analysis
Code: 17:18:48 UTC,
rb,
verify,
result: Passed
# you can write to stdout for debugging purposes, e.g.
# puts "this is a debug message"
def solution(a, b, k)
# write your code in Ruby 2.2
first = a + (a % k)
last = b - (b % k)
count = ((last - first) / k) + 1
return count
end
User test case 1:
[6, 11, 3]
Analysis
Code: 17:21:00 UTC,
rb,
verify,
result: Passed
# you can write to stdout for debugging purposes, e.g.
# puts "this is a debug message"
def solution(a, b, k)
# write your code in Ruby 2.2
first = a + (a % k)
last = b - (b % k)
count = ((last - first) / k) + 1
return count
end
User test case 1:
[6, 11, 3]
User test case 2:
[3, 20, 5]
Analysis
Code: 17:21:26 UTC,
rb,
verify,
result: Passed
# you can write to stdout for debugging purposes, e.g.
# puts "this is a debug message"
def solution(a, b, k)
# write your code in Ruby 2.2
first = a + (a % k)
puts first
last = b - (b % k)
count = ((last - first) / k) + 1
return count
end
User test case 1:
[6, 11, 3]
User test case 2:
[3, 20, 5]
Analysis
expand all
User tests
1.
0.097 s
OK
function result: 2
function result: 2
stdout:
6
1.
0.097 s
OK
function result: 3
function result: 3
stdout:
6
Code: 17:21:48 UTC,
rb,
verify,
result: Passed
# you can write to stdout for debugging purposes, e.g.
# puts "this is a debug message"
def solution(a, b, k)
# write your code in Ruby 2.2
first = a + (a % k)
puts first
last = b - (b % k)
puts last
count = ((last - first) / k) + 1
return count
end
User test case 1:
[6, 11, 3]
User test case 2:
[3, 20, 5]
Analysis
expand all
User tests
1.
0.098 s
OK
function result: 2
function result: 2
stdout:
6 9
1.
0.099 s
OK
function result: 3
function result: 3
stdout:
6 20
Code: 17:22:59 UTC,
rb,
verify,
result: Failed
# you can write to stdout for debugging purposes, e.g.
# puts "this is a debug message"
def solution(a, b, k)
# write your code in Ruby 2.2
first = (a + k - 1) / k
puts first
# Calculates the last divisible number in range
last = b - (b % k)
count = ((last - first) / k) + 1
return count
end
User test case 1:
[6, 11, 3]
User test case 2:
[3, 20, 5]
Analysis
expand all
Example tests
1.
0.100 s
WRONG ANSWER,
got 4 expected 3
stdout:
3
expand all
User tests
1.
0.099 s
OK
function result: 3
function result: 3
stdout:
2
1.
0.097 s
OK
function result: 4
function result: 4
stdout:
1
Code: 17:23:20 UTC,
rb,
verify,
result: Passed
# you can write to stdout for debugging purposes, e.g.
# puts "this is a debug message"
def solution(a, b, k)
# write your code in Ruby 2.2
first = ((a + k - 1) / k) * k
puts first
# Calculates the last divisible number in range
last = b - (b % k)
count = ((last - first) / k) + 1
return count
end
User test case 1:
[6, 11, 3]
User test case 2:
[3, 20, 5]
Analysis
expand all
User tests
1.
0.101 s
OK
function result: 2
function result: 2
stdout:
6
1.
0.100 s
OK
function result: 4
function result: 4
stdout:
5
Code: 17:27:41 UTC,
rb,
verify,
result: Passed
# you can write to stdout for debugging purposes, e.g.
# puts "this is a debug message"
def solution(a, b, k)
# write your code in Ruby 2.2
# Calculates the first divisible number in range
# First, sums the first number with k and subtract -1, so the division
# with k will never return k. (eg. a = 2, k = 2. 2 + 2 = 4; 4 - 1 = 3; 3 / 2 = 1.
# Multipling with k will give the next divisible number. (eg. 1 * k = 2)
first = ((a + k - 1) / k) * k
# Calculates the last divisible number in range
last = b - (b % k)
count = ((last - first) / k) + 1
return count
end
User test case 1:
[6, 11, 3]
User test case 2:
[3, 20, 5]
Analysis
Code: 17:27:46 UTC,
rb,
verify,
result: Passed
# you can write to stdout for debugging purposes, e.g.
# puts "this is a debug message"
def solution(a, b, k)
# write your code in Ruby 2.2
# Calculates the first divisible number in range
# First, sums the first number with k and subtract -1, so the division
# with k will never return k. (eg. a = 2, k = 2. 2 + 2 = 4; 4 - 1 = 3; 3 / 2 = 1.
# Multipling with k will give the next divisible number. (eg. 1 * k = 2)
first = ((a + k - 1) / k) * k
# Calculates the last divisible number in range
last = b - (b % k)
count = ((last - first) / k) + 1
return count
end
User test case 1:
[6, 11, 3]
User test case 2:
[3, 20, 5]
Analysis
Code: 17:27:49 UTC,
rb,
final,
score:
100
# you can write to stdout for debugging purposes, e.g.
# puts "this is a debug message"
def solution(a, b, k)
# write your code in Ruby 2.2
# Calculates the first divisible number in range
# First, sums the first number with k and subtract -1, so the division
# with k will never return k. (eg. a = 2, k = 2. 2 + 2 = 4; 4 - 1 = 3; 3 / 2 = 1.
# Multipling with k will give the next divisible number. (eg. 1 * k = 2)
first = ((a + k - 1) / k) * k
# Calculates the last divisible number in range
last = b - (b % k)
count = ((last - first) / k) + 1
return count
endAnalysis summary
The solution obtained perfect score.
Analysis
Detected time complexity:
O(1)
expand all
Correctness tests
1.
0.101 s
OK
1.
0.103 s
OK
2.
0.103 s
OK
1.
0.103 s
OK
2.
0.108 s
OK
3.
0.099 s
OK
1.
0.101 s
OK
2.
0.099 s
OK
3.
0.098 s
OK
4.
0.101 s
OK
5.
0.098 s
OK
6.
0.097 s
OK
expand all
Performance tests
1.
0.100 s
OK
1.
0.101 s
OK
1.
0.100 s
OK
2.
0.100 s
OK
1.
0.100 s
OK
2.
0.099 s
OK
3.
0.102 s
OK
4.
0.100 s
OK