## 2017年2月18日 星期六

### 【Python】Codility in Python : Lesson 5 - Prefix Sums【GenomicRangeQuery】

Prefix Sums 第三題：【GenomicRangeQuery】
Find the minimal nucleotide from a range of sequence DNA.
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:

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 = 2　　Q = 4
P = 5　　Q = 5
P = 0　　Q = 6

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

Correctness：100%、Performance：100%
```python mapping = {"A":100001, "C":100001, "G":100001} def solutionByMapping(S, P, Q): length = len(S) matrix = [( * length) for i in range(len(mapping))] for i in range(length-1, -1, -1): mapping[S[i]] = i matrix[i] = mapping['A'] matrix[i] = mapping['C'] matrix[i] = mapping['G'] length = len(P) result =  * length for i in range(length): if matrix[P[i]] <= Q[i]: result[i] = 1 elif matrix[P[i]] <= Q[i]: result[i] = 2 elif matrix[P[i]] <= Q[i]: result[i] = 3 else: result[i] = 4 return result ```

Correctness：100%、Performance：33%
```python def solutionBySlice(S, P, Q): result = [] length = len(P) for i in range(length): temp = (S[P[i]:Q[i]+1]) if "A" in temp: result.append(1) elif "C" in temp: result.append(2) elif "G" in temp: result.append(3) elif "T" in temp: result.append(4) return result ```