Codility : GenomicRangeQuery

 

GenomicRangeQuery

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:

def solution(S, P, Q)

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

The sequence should be returned as:

  • a Results structure (in C), or
  • a vector of integers (in C++), or
  • a Results record (in Pascal), or
  • an array of integers (in any other programming language).

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.

Assume that:

  • 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.

Complexity:

  • expected worst-case time complexity is O(N+M);
  • expected worst-case space complexity is O(N), beyond input storage (not counting the storage required for input arguments).

 Python Solution :

def solution(S, P, Q):
    # write your code in Python 2.7
    mapping={"A":1,"C":2,"G":3,"T":4}
    n=len(S)
    nucl_pos=[[-1]*n for i in range(0,4)]
    for i in range(n-1,-1,-1):
        if (i+1) <n:
            nucl_pos[0][i] = nucl_pos[0][i+1]
            nucl_pos[1][i] = nucl_pos[1][i+1]
            nucl_pos[2][i] = nucl_pos[2][i+1]
            nucl_pos[3][i] = nucl_pos[3][i+1]
        nucl_pos[mapping[S[i]]-1][i]=i
        
    
    results=[]
    for i in range(0,len(P)) : 
        if nucl_pos[0][P[i]]!=-1 and nucl_pos[0][P[i]] <=Q[i]:
            results.append(1)
        elif nucl_pos[1][P[i]]!=-1 and nucl_pos[1][P[i]] <=Q[i]:
            results.append(2)
        elif nucl_pos[2][P[i]]!=-1 and nucl_pos[2][P[i]] <=Q[i]:
            results.append(3)
        elif nucl_pos[3][P[i]]!=-1 and nucl_pos[3][P[i]] <=Q[i]:
            results.append(4)
            
    return results
email@djangotutsme.com April 6, 2016, 7:26 a.m.