GenomicRangeQuery

tab1

Task Score     :100
Correctness   :100
Performance : 100

Topic Title

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 Thave 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 Gand 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[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, 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

public class GenomicRangeQuery {

 public static void main(String[] args) {
  int[] P = { 2, 5, 0 };
  int[] Q = { 4, 5, 6 };
  System.out.println(new GenomicRangeQuery().solution("CAGCCTA", P, Q));
 }

 public int[] solution(String S, int[] P, int[] Q) {

  if (P.length != Q.length) {
   return new int[0];
  }
  
  int[][] count= new int[3][S.length()+1];
  for (int i = 0; i < S.length(); i++) {
   int a=0, c=0,g=0;
   if(S.charAt(i) == 'A') {
    a++;
   }else if(S.charAt(i) == 'C') {
    c++;
   }else if(S.charAt(i) == 'G') {
    g++;
   }
   // use prefix_sum , here we are incrementing the value fir current letter
   count[0][i+1] =count[0][i]+a;
   count[1][i+1] =count[1][i]+c;
   count[2][i+1] =count[2][i]+g;
  }
  
  int[] retVal = new int[P.length];
  for (int i = 0; i < P.length; i++) {
   if(P[i] > Q[i]) {
    return new int[0];
   }
   if(Q[i] >= S.length()) {
    return new int[0];
   }

   // here if difference for a perticular letter if non zero that meant it occured but we want to find letter with min value
   if((count[0][Q[i]+1] - count[0][P[i]]) > 0) {
    retVal[i] = 1;
   }else if((count[1][Q[i]+1] - count[1][P[i]]) > 0) {
    retVal[i] = 2;
   }
   else if((count[2][Q[i]+1] - count[2][P[i]]) > 0) {
    retVal[i] = 3;
   }else  {
    retVal[i] = 4;
   }
   
  }

  return retVal;
 }
}