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Tasks Details
medium
1.
CountDiv
Compute number of integers divisible by k in range [a..b].
Task Score
37%
Correctness
25%
Performance
50%
Task description
Write a function:
class Solution { public int solution(int A, int B, int 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 Java 21
Time spent on task 15 minutes
Notes
not defined yet
Task timeline
Code: 08:33:48 UTC,
java,
verify,
result: Failed
// you can also use imports, for example:
// import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int A, int B, int K) {
// write your code in Java SE 8
int start;
if(B<A || K==0 || K>B )
return 0;
else if(K<A)
start = A%K +1;
else if (K<=B)
start = K;
return (B-start+1)/K+ 1;
}
}
Analysis
Compile error
Solution.java:21: error: variable start might not have been initialized
return (B-start+1)/K+ 1;
^
1 error
Code: 08:34:04 UTC,
java,
verify,
result: Failed
// you can also use imports, for example:
// import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int A, int B, int K) {
// write your code in Java SE 8
int start=0;;
if(B<A || K==0 || K>B )
return 0;
else if(K<A)
start = A%K +1;
else if (K<=B)
start = K;
return (B-start+1)/K+ 1;
}
}
Analysis
expand all
Example tests
1.
0.868 s
WRONG ANSWER,
got 6 expected 3
Code: 08:36:11 UTC,
java,
verify,
result: Failed
// you can also use imports, for example:
// import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int A, int B, int K) {
// write your code in Java SE 8
int start=0;;
if(B<A || K==0 || K>B )
return 0;
else if(K<A)
start =K* ( A%K +1);
else if (K<=B)
start = K;
return (B-start+1)/K+ 1;
}
}
Analysis
expand all
Example tests
1.
1.252 s
WRONG ANSWER,
got 6 expected 3
Code: 08:36:40 UTC,
java,
verify,
result: Failed
// you can also use imports, for example:
// import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int A, int B, int K) {
// write your code in Java SE 8
int start=0;;
if(B<A || K==0 || K>B )
return 0;
else if(K<A)
start =K* ( A%K );
else if (K<=B)
start = K;
return (B-start+1)/K+ 1;
}
}
Analysis
expand all
Example tests
1.
1.500 s
WRONG ANSWER,
got 7 expected 3
Code: 08:39:13 UTC,
java,
verify,
result: Failed
// you can also use imports, for example:
// import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int A, int B, int K) {
// write your code in Java SE 8
int start=0;;
if(B<A || K==0 || K>B )
return 0;
else if(K<A){
start = K * ( A%K );
system.out.println("coucou"+start);
}
else if (K<=B)
start = K;
return (B-start+1)/K+ 1;
}
}
Analysis
Compile error
Solution.java:18: error: package system does not exist
system.out.println("coucou"+start);
^
1 error
Code: 08:39:29 UTC,
java,
verify,
result: Failed
// you can also use imports, for example:
// import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int A, int B, int K) {
// write your code in Java SE 8
int start=0;;
if(B<A || K==0 || K>B )
return 0;
else if(K<A){
start = K * ( A%K );
System.out.println("coucou"+start);
}
else if (K<=B)
start = K;
return (B-start+1)/K+ 1;
}
}
Analysis
expand all
Example tests
1.
1.568 s
WRONG ANSWER,
got 7 expected 3
stdout:
coucou0
Code: 08:40:59 UTC,
java,
verify,
result: Failed
// you can also use imports, for example:
// import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int A, int B, int K) {
// write your code in Java SE 8
int start=0;;
if(B<A || K==0 || K>B )
return 0;
else if(K<A){
start = K * ( A/K );
System.out.println("coucou"+start);
}
else if (K<=B)
start = K;
return (B-start+1)/K+ 1;
}
}
Analysis
expand all
Example tests
1.
1.300 s
WRONG ANSWER,
got 4 expected 3
stdout:
coucou6
Code: 08:41:30 UTC,
java,
verify,
result: Passed
// you can also use imports, for example:
// import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int A, int B, int K) {
// write your code in Java SE 8
int start=0;;
if(B<A || K==0 || K>B )
return 0;
else if(K<A){
start = K * ( A/K +1);
System.out.println("coucou"+start);
}
else if (K<=B)
start = K;
return (B-start+1)/K+ 1;
}
}
Analysis
expand all
Example tests
1.
1.332 s
OK
stdout:
WARNING: producing output may seriously slow down your code! coucou8
Code: 08:42:23 UTC,
java,
verify,
result: Passed
// you can also use imports, for example:
// import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int A, int B, int K) {
// write your code in Java SE 8
int start=0;;
if(B<A || K==0 || K>B )
return 0;
else if(K<A){
start = K * ( A/K +1);
//System.out.println("coucou"+start);
}
else if (K<=B)
start = K;
return (B-start+1)/K+ 1;
}
}
Analysis
Code: 08:42:31 UTC,
java,
final,
score:
37
// you can also use imports, for example:
// import java.util.*;
// you can use System.out.println for debugging purposes, e.g.
// System.out.println("this is a debug message");
class Solution {
public int solution(int A, int B, int K) {
// write your code in Java SE 8
int start=0;;
if(B<A || K==0 || K>B )
return 0;
else if(K<A){
start = K * ( A/K +1);
//System.out.println("coucou"+start);
}
else if (K<=B)
start = K;
return (B-start+1)/K+ 1;
}
}Analysis summary
The following issues have been detected: wrong answers.
Analysis
expand all
Correctness tests
1.
1.616 s
OK
1.
1.492 s
WRONG ANSWER,
got 0 expected 1
1.
1.456 s
WRONG ANSWER,
got 1 expected 0
extreme_endpoints
verify handling of range endpoints, multiple runs
verify handling of range endpoints, multiple runs
✘
WRONG ANSWER
got 2 expected 3
got 2 expected 3
1.
1.388 s
WRONG ANSWER,
got 2 expected 3
expand all
Performance tests
1.
1.476 s
OK
1.
1.428 s
OK
1.
1.416 s
WRONG ANSWER,
got 1 expected 2
1.
1.488 s
WRONG ANSWER,
got 2 expected 1