Test results - Codility

Tasks Details

medium

1. MissingInteger

Find the smallest positive integer that does not occur in a given sequence.

100%

This is a demo task.

Write a function:

object Solution { def solution(a: Array[Int]): Int }

that, given an array A of N integers, returns the smallest positive integer (greater than 0) that does not occur in A.

For example, given A = [1, 3, 6, 4, 1, 2], the function should return 5.

Given A = [1, 2, 3], the function should return 4.

Given A = [−1, −3], the function should return 1.

Write an efficient algorithm for the following assumptions:

N is an integer within the range [1..100,000];

each element of array A is an integer within the range [−1,000,000..1,000,000].

Solution

Programming language used Scala

Time spent on task 7 minutes

Notes

not defined yet

Task timeline

Code: 02:28:51 UTC, scala, verify, result: Passed

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

import scala.collection.JavaConversions._

// you can use println for debugging purposes, e.g.
// println("this is a debug message")

object Solution {
    def solution(A: Array[Int]): Int = {
        // First build set of integers that exist.
        @scala.annotation.tailrec
        def buildSet(index: Int, accum: Set[Int]): Set[Int] = {
            if (index >= A.length) accum
            else {
                val nextValue = A(index)
                val nextAccum = 
                    if (nextValue > 0) accum + nextValue
                    else accum
                buildSet(index + 1, nextAccum)
            }
        }
        val positiveValues = buildSet(0, Set.empty)
        
        // Next find lowest number not in set.
        @scala.annotation.tailrec
        def findLowest(i: Int): Int = {
            if (positiveValues contains i) findLowest(i + 1)
            else i
        }
        
        findLowest(1)
    }
}

Analysis

▶

example
example (without minus)

✔

Code: 02:29:30 UTC, scala, verify, result: Passed

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

import scala.collection.JavaConversions._

// you can use println for debugging purposes, e.g.
// println("this is a debug message")

object Solution {
    def solution(A: Array[Int]): Int = {
        // First build set of integers that exist.
        @scala.annotation.tailrec
        def buildSet(index: Int, accum: Set[Int]): Set[Int] = {
            if (index >= A.length) accum
            else {
                val nextValue = A(index)
                val nextAccum = 
                    if (nextValue > 0) accum + nextValue
                    else accum
                buildSet(index + 1, nextAccum)
            }
        }
        val positiveValues = buildSet(0, Set.empty)
        
        // Next find lowest number not in set.
        @scala.annotation.tailrec
        def findLowest(i: Int): Int = {
            if (positiveValues contains i) findLowest(i + 1)
            else i
        }
        
        findLowest(1)
    }
}

Analysis

▶

example
example (without minus)

✔

Code: 02:29:44 UTC, scala, final, score: 100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

import scala.collection.JavaConversions._

// you can use println for debugging purposes, e.g.
// println("this is a debug message")

object Solution {
    def solution(A: Array[Int]): Int = {
        // First build set of integers that exist.
        @scala.annotation.tailrec
        def buildSet(index: Int, accum: Set[Int]): Set[Int] = {
            if (index >= A.length) accum
            else {
                val nextValue = A(index)
                val nextAccum = 
                    if (nextValue > 0) accum + nextValue
                    else accum
                buildSet(index + 1, nextAccum)
            }
        }
        val positiveValues = buildSet(0, Set.empty)
        
        // Next find lowest number not in set.
        @scala.annotation.tailrec
        def findLowest(i: Int): Int = {
            if (positiveValues contains i) findLowest(i + 1)
            else i
        }
        
        findLowest(1)
    }
}

Analysis summary

The solution obtained perfect score.

Analysis

Detected time complexity:

O(N)

▶

example
example (without minus)

✔

▶

extreme_single
a single element

✔

▶

simple
simple test

✔

▶

extreme_min_max_int
MININT and MAXINT (with minus)

✔

▶

positive_only
shuffled sequence of 0...100 and then 102...200

✔

▶

negative_only
shuffled sequence -100 ... -1

✔

▶

medium
chaotic sequences length=10005 (with minus)

✔

▶

large_1
chaotic + sequence 1, 2, ..., 40000 (without minus)

✔

▶

large_2
shuffled sequence 1, 2, ..., 100000 (without minus)

✔

▶

large_3
chaotic + many -1, 1, 2, 3 (with minus)

✔