# Codility's GenomicRangeQuery solution in C#

I've been learning C# for a few months now, and I've done some basic things in java last year. I made a solution for the problem the title states, this is the task description.

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 = SS...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 = 2    Q = 4
P = 5    Q = 5
P = 0    Q = 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:

class Solution { public int[] solution(string S, int[] P, int[] 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 = 2    Q = 4
P = 5    Q = 5
P = 0    Q = 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, 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.

This is my 100% task score solution in C#. What things can be improved?

/// <summary>
/// Find the minimum impact factor for every query in a given chain
/// </summary>
/// <returns>
/// An array of ints, every int represents the minimum impact factor found
/// within ranges in a given chain
/// </returns>
public int[] GetMinimumImpactFactors(string S, int[] P, int[] Q)
{
//nuc(s) is short for nucleotide(s)
Dictionary<char, int> nucsDict = new Dictionary<char, int>(){{'A',1},{'C',2},{'G',3},{'T',4}};
int[] result = new int[P.Length];
int[] nucsInOrder= new int[S.Length];
int nucsIndex = 0;
//iterate through dictionary, looking for A's, then C's, and so on...
foreach ( var searchedImpactPair in nucsDict )
{
//Appearances of <searchedImpactPair.Key> have a given position in <S> chain, those positions are saved
for (int currNucPos=0; currNucPos < S.Length; currNucPos++ )
{
if( S[currNucPos] == searchedImpactPair.Key )
{
nucsInOrder[nucsIndex++] = currNucPos ;
}
}
}
int start, end, minImpactValueFound, minNucFound;
char nucleotide;
for(int positionWithinRange = 0; positionWithinRange < P.Length; positionWithinRange++)
{

start = P[positionWithinRange];
end = Q[positionWithinRange];
for ( int nucInOrder = 0; nucInOrder < nucsInOrder.Length; nucInOrder++ )
{
minNucFound = nucsInOrder[nucInOrder];
if ( minNucFound >= start && nucsInOrder[nucInOrder] <= end)
{
nucleotide = S[minNucFound];
minImpactValueFound = nucsDict[nucleotide];
result[positionWithinRange] = minImpactValueFound;
break;
}
}
}
return result;
}