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:
int solution(vector<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 2009–2024 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
Solution
Programming language used C++
Total time used 7 minutes
Effective time used 7 minutes
Notes
not defined yet
Task timeline
Code: 16:32:58 UTC,
cpp,
verify,
result: Failed
// you can use includes, for example:
// #include <algorithm>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;
int solution(vector<int> &A) {
// write your code in C++11
if ( A.empty() )
{
return 1;
}
unsigned int actualsum = A[0];
int N = A.size()+1;
unsigned int nonmissingsum = N*(N+1)/2;
for (size_t i = 1; i < A.size(); i++)
{
actualsum += A[i];
}
return (nonmissingsum - actualsum;)
}
Analysis
Compile error
In file included from user.cpp:21:0: func.cpp: In function 'int solution(std::vector<int>&)': func.cpp:23:38: error: expected ')' before ';' token return (nonmissingsum - actualsum;) ^ func.cpp:23:39: error: expected primary-expression before ')' token return (nonmissingsum - actualsum;) ^ func.cpp:23:39: error: expected ';' before ')' token
Code: 16:33:07 UTC,
cpp,
verify,
result: Failed
// you can use includes, for example:
// #include <algorithm>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;
int solution(vector<int> &A) {
// write your code in C++11
if ( A.empty() )
{
return 1;
}
unsigned int actualsum = A[0];
int N = A.size()+1;
unsigned int nonmissingsum = N*(N+1)/2;
for (size_t i = 1; i < A.size(); i++)
{
actualsum += A[i];
}
return (nonmissingsum - actualsum;)
}
Analysis
Compile error
In file included from user.cpp:21:0: func.cpp: In function 'int solution(std::vector<int>&)': func.cpp:23:38: error: expected ')' before ';' token return (nonmissingsum - actualsum;) ^ func.cpp:23:39: error: expected primary-expression before ')' token return (nonmissingsum - actualsum;) ^ func.cpp:23:39: error: expected ';' before ')' token
Code: 16:33:25 UTC,
cpp,
verify,
result: Passed
// you can use includes, for example:
// #include <algorithm>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;
int solution(vector<int> &A) {
// write your code in C++11
if ( A.empty() )
{
return 1;
}
unsigned int actualsum = A[0];
int N = A.size()+1;
unsigned int nonmissingsum = N*(N+1)/2;
for (size_t i = 1; i < A.size(); i++)
{
actualsum += A[i];
}
return (nonmissingsum - actualsum);
}
User test case 1:
None
Analysis
Code: 16:33:46 UTC,
cpp,
verify,
result: Passed
// you can use includes, for example:
// #include <algorithm>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;
int solution(vector<int> &A) {
// write your code in C++11
if ( A.empty() )
{
return 1;
}
unsigned int actualsum = A[0];
int N = A.size()+1;
unsigned int nonmissingsum = N*(N+1)/2;
for (size_t i = 1; i < A.size(); i++)
{
actualsum += A[i];
}
return (nonmissingsum - actualsum);
}
User test case 1:
None
Analysis
Code: 16:34:02 UTC,
cpp,
verify,
result: Passed
// you can use includes, for example:
// #include <algorithm>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;
int solution(vector<int> &A) {
// write your code in C++11
if ( A.empty() )
{
return 1;
}
unsigned int actualsum = A[0];
int N = A.size()+1;
unsigned int nonmissingsum = N*(N+1)/2;
for (size_t i = 1; i < A.size(); i++)
{
actualsum += A[i];
}
return (nonmissingsum - actualsum);
}
User test case 1:
None
Analysis
Code: 16:34:07 UTC,
cpp,
final,
score: 
80
// you can use includes, for example:
// #include <algorithm>
// you can write to stdout for debugging purposes, e.g.
// cout << "this is a debug message" << endl;
int solution(vector<int> &A) {
// write your code in C++11
if ( A.empty() )
{
return 1;
}
unsigned int actualsum = A[0];
int N = A.size()+1;
unsigned int nonmissingsum = N*(N+1)/2;
for (size_t i = 1; i < A.size(); i++)
{
actualsum += A[i];
}
return (nonmissingsum - actualsum);
}
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.
0.012 s
OK
1.
0.012 s
OK
1.
0.032 s
WRONG ANSWER,
got -2147483647 expected 1
1.
0.048 s
OK
1.
0.036 s
WRONG ANSWER,
got -2147473647 expected 10001