Tasks Details
easy
Find the missing element in a given permutation.
Task Score
80%
Correctness
100%
Performance
60%
An array A consisting of N different integers is given. The array contains integers in the range [1..(N + 1)], which means that exactly one element is missing.
Your goal is to find that missing element.
Write a function:
class Solution { public int solution(int[] A); }
that, given an array A, returns the value of the missing element.
For example, given array A such that:
A[0] = 2 A[1] = 3 A[2] = 1 A[3] = 5the function should return 4, as it is the missing element.
Write an efficient algorithm for the following assumptions:
- N is an integer within the range [0..100,000];
- the elements of A are all distinct;
- each element of array A is an integer within the range [1..(N + 1)].
Copyright 2009–2025 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
Solution
Programming language used Java 8
Time spent on task 23 minutes
Notes
not defined yet
Code: 18:47:19 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) {
long nPlusOneSum = (A.length + 2) * (A.length + 1) / 2;
long arraySum = 0;
for (int element : A)
arraySum += element;
return nPlusOneSum - arraySum;
}
Analysis
Compile error
Solution.java:14: error: reached end of file while parsing } ^ 1 error
Code: 18:47:39 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) {
long nPlusOneSum = (A.length + 2) * (A.length + 1) / 2;
long arraySum = 0;
for (int element : A)
arraySum += element;
return nPlusOneSum - arraySum;
}
Analysis
Compile error
Solution.java:14: error: reached end of file while parsing } ^ 1 error
Code: 18:47:55 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) {
long nPlusOneSum = (A.length + 2) * (A.length + 1) / 2;
long arraySum = 0;
for (int element : A)
arraySum += element;
return nPlusOneSum - arraySum;
}
Analysis
Compile error
Solution.java:14: error: reached end of file while parsing } ^ 1 error
Code: 18:48:16 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) {
long nPlusOneSum = (A.length + 2) * (A.length + 1) / 2;
long arraySum = 0;
for (int element : A)
arraySum += element;
return nPlusOneSum - arraySum;
}
}
Analysis
Compile error
Solution.java:13: error: incompatible types: possible lossy conversion from long to int
return nPlusOneSum - arraySum;
^
1 error
Code: 18:48:40 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) {
long nPlusOneSum = (A.length + 2) * (A.length + 1) / 2;
long arraySum = 0;
for (int element : A)
arraySum += element;
return (int) nPlusOneSum - arraySum;
}
}
Analysis
Compile error
Solution.java:13: error: incompatible types: possible lossy conversion from long to int
return (int) nPlusOneSum - arraySum;
^
1 error
Code: 18:54:18 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) {
long nPlusOneSum = (A.length + 2) * (A.length + 1) / 2;
long arraySum = 0L;
for (int element : A)
arraySum += element;
return (int) nPlusOneSum - arraySum;
}
}
Analysis
Compile error
Solution.java:13: error: incompatible types: possible lossy conversion from long to int
return (int) nPlusOneSum - arraySum;
^
1 error
Code: 18:54:36 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) {
long nPlusOneSum = (A.length + 2) * (A.length + 1) / 2;
long arraySum = 0L;
for (int element : A)
arraySum += element;
return (int) (nPlusOneSum - arraySum);
}
}
Analysis
Code: 18:54:45 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) {
long nPlusOneSum = (A.length + 2) * (A.length + 1) / 2;
long arraySum = 0L;
for (int element : A)
arraySum += element;
return (int) (nPlusOneSum - arraySum);
}
}
Analysis
Code: 18:54:53 UTC,
java,
final,
score:
80
// 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) {
long nPlusOneSum = (A.length + 2) * (A.length + 1) / 2;
long arraySum = 0L;
for (int element : A)
arraySum += element;
return (int) (nPlusOneSum - arraySum);
}
}Analysis summary
The following issues have been detected: wrong answers.
Analysis
Detected time complexity:
O(N) or O(N * log(N))
expand all
Performance tests
1.
0.940 s
OK
1.
1.516 s
OK
1.
1.692 s
WRONG ANSWER,
got -2147483647 expected 1
1.
1.580 s
OK
1.
1.644 s
WRONG ANSWER,
got -2147473647 expected 10001