Problema:

A non-empty zero-indexed array A consisting of N integers is given. Array A represents numbers on a tape.

Any integer P, such that 0 < P < N, splits this tape into two non-empty parts: A[0], A[1], …, A[P − 1] and A[P], A[P + 1], …, A[N − 1].

The difference between the two parts is the value of: |(A[0] + A[1] + … + A[P − 1]) − (A[P] + A[P + 1] + … + A[N − 1])|

In other words, it is the absolute difference between the sum of the first part and the sum of the second part.

For example, consider array A such that:

A[0] = 3 A[1] = 1 A[2] = 2 A[3] = 4 A[4] = 3

We can split this tape in four places:

  • P = 1, difference = |3 − 10| = 7
  • P = 2, difference = |4 − 9| = 5
  • P = 3, difference = |6 − 7| = 1
  • P = 4, difference = |10 − 3| = 7

Write a function:

def solution(A)

that, given a non-empty zero-indexed array A of N integers, returns the minimal difference that can be achieved.

For example, given:

A[0] = 3 A[1] = 1 A[2] = 2 A[3] = 4 A[4] = 3

the function should return 1, as explained above.

Assume that:

  • N is an integer within the range [2..100,000];
  • each element of array A is an integer within the range [−1,000..1,000].

Complexity:

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

Elements of input arrays can be modified.

Solución:


def solution(A):
    minimal = 0
    right_part = sum(A)
    left_part = 0
    for x in xrange(len(A)-1):
        left_part += A[x]
        right_part -= A[x]
        difference = abs(left_part - right_part)
        if minimal == 0 or difference < minimal:
            minimal = difference
    return minimal

Este problema nos dice que dado una lista A tomemos la diferencia absoluta entre la parte izquierda y la derecha, ejemplo si A = [3, 1, 2, 4, 3]

  • (3) – (1+2+4+3) = 7
  • (3+1) – (2+4+3) = 5
  • (3+1+2)-(4+3) = 1
  • (3+1+2+4) – (3) = 7

Y al final retornamos la mínima diferencia, en este caso 1.

Lamentablemente en este problema obtuve 83% y no pude llegar a 100% (100% correctness y 66% performance), espero y alguien tenga una mejor solución.

Aquí esta el repo con todas mis soluciones de codility: https://github.com/OmarIbannez/codility-lessons

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