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Tasks Details
easy
Find value that occurs in odd number of elements.
Task Score
100%
Correctness
100%
Performance
100%
Task description
A non-empty array A consisting of N integers is given. The array contains an odd number of elements, and each element of the array can be paired with another element that has the same value, except for one element that is left unpaired.
For example, in array A such that:
A[0] = 9 A[1] = 3 A[2] = 9 A[3] = 3 A[4] = 9 A[5] = 7 A[6] = 9
- the elements at indexes 0 and 2 have value 9,
- the elements at indexes 1 and 3 have value 3,
- the elements at indexes 4 and 6 have value 9,
- the element at index 5 has value 7 and is unpaired.
Write a function:
function solution(A);
that, given an array A consisting of N integers fulfilling the above conditions, returns the value of the unpaired element.
For example, given array A such that:
A[0] = 9 A[1] = 3 A[2] = 9 A[3] = 3 A[4] = 9 A[5] = 7 A[6] = 9the function should return 7, as explained in the example above.
Write an efficient algorithm for the following assumptions:
- N is an odd integer within the range [1..1,000,000];
- each element of array A is an integer within the range [1..1,000,000,000];
- all but one of the values in A occur an even number of times.
Copyright 2009–2025 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
Solution
Programming language used JavaScript
Time spent on task 15 minutes
Notes
not defined yet
Task timeline
Code: 18:21:59 UTC,
java,
autosave
Code: 18:22:10 UTC,
js,
autosave
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
let hash = new Map();
for(let i = 0; i < A.length; ++i) {
hash.set(A[i], !!!hash.has(A[i]));
}
let unpairedElement = 0;
hash.forEach((value, key) => {
if (value) {
unpairedElement = key;
}
});
return unpairedElement;
}
Code: 18:22:14 UTC,
js,
verify,
result: Passed
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
let hash = new Map();
for(let i = 0; i < A.length; ++i) {
hash.set(A[i], !!!hash.has(A[i]));
}
let unpairedElement = 0;
hash.forEach((value, key) => {
if (value) {
unpairedElement = key;
}
});
return unpairedElement;
}
Analysis
User test case 1:
[1, 2, 2, 2, 2]
Code: 18:22:21 UTC,
js,
verify,
result: Passed
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
let hash = new Map();
for(let i = 0; i < A.length; ++i) {
hash.set(A[i], !!!hash.has(A[i]));
}
let unpairedElement = 0;
hash.forEach((value, key) => {
if (value) {
unpairedElement = key;
}
});
return unpairedElement;
}
Analysis
User test case 1:
[1, 2, 2, 2, 2, 1, 3]
Code: 18:34:57 UTC,
js,
autosave
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
let hash = new Map();
for(let i = 0; i < A.length; ++i) {
hash.set(A[i], !!!hash.has(A[i]));
}
let unpairedElement = 0;
hash.forEach((value, key) => {
if (value) {
unpairedElement = key;
}
});
return unpairedElement;
}
Code: 18:34:59 UTC,
js,
verify,
result: Passed
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
let hash = new Map();
for(let i = 0; i < A.length; ++i) {
hash.set(A[i], !!!hash.has(A[i]));
}
let unpairedElement = 0;
hash.forEach((value, key) => {
if (value) {
unpairedElement = key;
}
});
return unpairedElement;
}
Analysis
User test case 1:
[1, 1, 1]
Code: 18:35:27 UTC,
js,
autosave
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
let hash = new Map();
for(let i = 0; i < A.length; ++i) {
hash.set(A[i], !!!hash.has(A[i]));
}
let unpairedElement = 0;
consoe.
hash.forEach((value, key) => {
if (value) {
unpairedElement = key;
}
});
return unpairedElement;
}
Code: 18:35:31 UTC,
js,
verify,
result: Passed
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
let hash = new Map();
for(let i = 0; i < A.length; ++i) {
hash.set(A[i], !!!hash.has(A[i]));
}
let unpairedElement = 0;
console.log(hash)
hash.forEach((value, key) => {
if (value) {
unpairedElement = key;
}
});
return unpairedElement;
}
Analysis
expand all
Example tests
1.
0.076 s
OK
stdout:
Map { 9 => false, 3 => false, 7 => true }
User test case 1:
[1, 1, 1]
Code: 18:35:49 UTC,
js,
verify,
result: Passed
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
let hash = new Map();
for(let i = 0; i < A.length; ++i) {
hash.set(A[i], !!!hash.has(A[i]));
console.log(hash.get(A[i]))
}
let unpairedElement = 0;
console.log(hash)
hash.forEach((value, key) => {
if (value) {
unpairedElement = key;
}
});
return unpairedElement;
}
Analysis
expand all
Example tests
1.
0.076 s
OK
stdout:
true
true
false
false
false
true
false
Map { 9 => false, 3 => false, 7 => true }
expand all
User tests
1.
0.072 s
OK
function result: 0
function result: 0
stdout:
true
false
false
Map { 1 => false }
User test case 1:
[1, 1, 1]
Code: 18:36:03 UTC,
js,
autosave
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
let hash = new Map();
for(let i = 0; i < A.length; ++i) {
hash.set(A[i], !!!hash.get(A[i]));
console.log(hash.get(A[i]))
}
let unpairedElement = 0;
console.log(hash)
hash.forEach((value, key) => {
if (value) {
unpairedElement = key;
}
});
return unpairedElement;
}
Code: 18:36:05 UTC,
js,
verify,
result: Passed
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
let hash = new Map();
for(let i = 0; i < A.length; ++i) {
hash.set(A[i], !!!hash.get(A[i]));
console.log(hash.get(A[i]))
}
let unpairedElement = 0;
console.log(hash)
hash.forEach((value, key) => {
if (value) {
unpairedElement = key;
}
});
return unpairedElement;
}
Analysis
expand all
Example tests
1.
0.076 s
OK
stdout:
true
true
false
false
true
true
false
Map { 9 => false, 3 => false, 7 => true }
expand all
User tests
1.
0.076 s
OK
function result: 1
function result: 1
stdout:
true
false
true
Map { 1 => true }
User test case 1:
[1, 1, 1]
Code: 18:36:13 UTC,
js,
autosave
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
let hash = new Map();
for(let i = 0; i < A.length; ++i) {
hash.set(A[i], !!!hash.get(A[i]));
}
let unpairedElement = 0;
console.log(hash)
hash.forEach((value, key) => {
if (value) {
unpairedElement = key;
}
});
return unpairedElement;
}
Code: 18:36:15 UTC,
js,
verify,
result: Passed
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
let hash = new Map();
for(let i = 0; i < A.length; ++i) {
hash.set(A[i], !!!hash.get(A[i]));
}
let unpairedElement = 0;
hash.forEach((value, key) => {
if (value) {
unpairedElement = key;
}
});
return unpairedElement;
}
Analysis
User test case 1:
[1, 1, 1]
Code: 18:36:18 UTC,
js,
final,
score:
100
// you can write to stdout for debugging purposes, e.g.
// console.log('this is a debug message');
function solution(A) {
// write your code in JavaScript (Node.js 8.9.4)
let hash = new Map();
for(let i = 0; i < A.length; ++i) {
hash.set(A[i], !!!hash.get(A[i]));
}
let unpairedElement = 0;
hash.forEach((value, key) => {
if (value) {
unpairedElement = key;
}
});
return unpairedElement;
}
Analysis summary
The solution obtained perfect score.
Analysis
Detected time complexity:
O(N) or O(N*log(N))