Test results - Codility

Tasks Details

medium

1. GenomicRangeQuery

Find the minimal nucleotide from a range of sequence DNA.

100%

A DNA sequence can be represented as a string consisting of the letters A, C, G and T, which correspond to the types of successive nucleotides in the sequence. Each nucleotide has an impact factor, which is an integer. Nucleotides of types A, C, G and T have impact factors of 1, 2, 3 and 4, respectively. You are going to answer several queries of the form: What is the minimal impact factor of nucleotides contained in a particular part of the given DNA sequence?

The DNA sequence is given as a non-empty string S = S[0]S[1]...S[N-1] consisting of N characters. There are M queries, which are given in non-empty arrays P and Q, each consisting of M integers. The K-th query (0 ≤ K < M) requires you to find the minimal impact factor of nucleotides contained in the DNA sequence between positions P[K] and Q[K] (inclusive).

For example, consider string S = CAGCCTA and arrays P, Q such that:

P[0] = 2 Q[0] = 4 P[1] = 5 Q[1] = 5 P[2] = 0 Q[2] = 6

The answers to these M = 3 queries are as follows:

The part of the DNA between positions 2 and 4 contains nucleotides G and C (twice), whose impact factors are 3 and 2 respectively, so the answer is 2.

The part between positions 5 and 5 contains a single nucleotide T, whose impact factor is 4, so the answer is 4.

The part between positions 0 and 6 (the whole string) contains all nucleotides, in particular nucleotide A whose impact factor is 1, so the answer is 1.

Write a function:

function solution(S, P, Q);

that, given a non-empty string S consisting of N characters and two non-empty arrays P and Q consisting of M integers, returns an array consisting of M integers specifying the consecutive answers to all queries.

Result array should be returned as an array of integers.

For example, given the string S = CAGCCTA and arrays P, Q such that:

P[0] = 2 Q[0] = 4 P[1] = 5 Q[1] = 5 P[2] = 0 Q[2] = 6

the function should return the values [2, 4, 1], as explained above.

Write an efficient algorithm for the following assumptions:

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

M is an integer within the range [1..50,000];

each element of arrays P and Q is an integer within the range [0..N - 1];

P[K] ≤ Q[K], where 0 ≤ K < M;

string S consists only of upper-case English letters A, C, G, T.

Solution

Programming language used JavaScript

Time spent on task 1 minutes

Notes

not defined yet

Task timeline

Code: 16:14:36 UTC, js, verify, result: Passed

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function solution(S, P, Q) {
    // Implement your solution here
    //factor = {'A':1,'C':2,'G':3,'T':4}
    var length_M = Math.min(P.length, Q.length)
    var M = []
    var showTimes = []
    var currentShowTime =  {'A':0,'C':0,'G':0,'T':0}
    for( var i = 0 ; i < S.length; i++){
        currentShowTime[S[i]]++
        showTimes.push({'A':currentShowTime['A'],'C':currentShowTime['C'],'G':currentShowTime['G'],'T':currentShowTime['T']})
    }
    //console.log(showTimes)
    for( var i = 0 ; i < length_M; i++){
        //var inclusive_S = S.slice(P[i], Q[i]+1).split("")
        //console.log(inclusive_S)
        if(P[i] == Q[i]){
            var factor = {'A':1,'C':2,'G':3,'T':4}
            M.push(factor[S[P[i]]])
        }else{
            var showTimesMax = showTimes[Q[i]]
            var showTimesMin = P[i] == 0 ? {'A':0,'C':0,'G':0,'T':0}:showTimes[P[i]-1]
            //console.log(showTimesMax, showTimesMin)
            if(showTimesMax['A'] - showTimesMin['A'] > 0) M.push(1)
            else if(showTimesMax['C'] - showTimesMin['C'] > 0) M.push(2)
            else if(showTimesMax['G'] - showTimesMin['G'] > 0) M.push(3)
            else M.push(4)
        }
    }
    return M
}

Analysis

▶

example
example test

✔

Code: 16:14:39 UTC, js, final, score: 100

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function solution(S, P, Q) {
    // Implement your solution here
    //factor = {'A':1,'C':2,'G':3,'T':4}
    var length_M = Math.min(P.length, Q.length)
    var M = []
    var showTimes = []
    var currentShowTime =  {'A':0,'C':0,'G':0,'T':0}
    for( var i = 0 ; i < S.length; i++){
        currentShowTime[S[i]]++
        showTimes.push({'A':currentShowTime['A'],'C':currentShowTime['C'],'G':currentShowTime['G'],'T':currentShowTime['T']})
    }
    //console.log(showTimes)
    for( var i = 0 ; i < length_M; i++){
        //var inclusive_S = S.slice(P[i], Q[i]+1).split("")
        //console.log(inclusive_S)
        if(P[i] == Q[i]){
            var factor = {'A':1,'C':2,'G':3,'T':4}
            M.push(factor[S[P[i]]])
        }else{
            var showTimesMax = showTimes[Q[i]]
            var showTimesMin = P[i] == 0 ? {'A':0,'C':0,'G':0,'T':0}:showTimes[P[i]-1]
            //console.log(showTimesMax, showTimesMin)
            if(showTimesMax['A'] - showTimesMin['A'] > 0) M.push(1)
            else if(showTimesMax['C'] - showTimesMin['C'] > 0) M.push(2)
            else if(showTimesMax['G'] - showTimesMin['G'] > 0) M.push(3)
            else M.push(4)
        }
    }
    return M
}

Analysis summary

The solution obtained perfect score.

Analysis

Detected time complexity:

O(N + M)

▶

example
example test

✔

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extreme_sinlge
single character string

✔

▶

extreme_double
double character string

✔

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simple
simple tests

✔

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small_length_string
small length simple string

✔

▶

small_random
small random string, length = ~300

✔

▶

almost_all_same_letters
GGGGGG..??..GGGGGG..??..GGGGGG

✔

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large_random
large random string, length

✔

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extreme_large
all max ranges

✔