Kate (cartonka) wrote,
Kate
cartonka

Greedy algorithms



Начала раздел про greedy algorithms, как они по-русски - жадные?))) В общем, это оказалось не такой сложной темой, как я ожидала. Первая задача была реально простой, но все равно приятно получить 100% за десять минут)) эх, были бы все алгоритмы такие простые. А то я параллельно читаю про heap sorting, и это кошмар как сложно. Но очень изящно и красиво. 


There are N ropes numbered from 0 to N − 1, whose lengths are given in an array A, lying on the floor in a line. For each I (0 ≤ I < N), the length of rope I on the line is A[I].

We say that two ropes I and I + 1 are adjacent. Two adjacent ropes can be tied together with a knot, and the length of the tied rope is the sum of lengths of both ropes. The resulting new rope can then be tied again.

For a given integer K, the goal is to tie the ropes in such a way that the number of ropes whose length is greater than or equal to K is maximal.

For example, consider K = 4 and array A such that:

A[0] = 1
A[1] = 2
A[2] = 3
A[3] = 4
A[4] = 1
A[5] = 1
A[6] = 3
The ropes are shown in the figure below.



We can tie:

rope 1 with rope 2 to produce a rope of length A[1] + A[2] = 5;
rope 4 with rope 5 with rope 6 to produce a rope of length A[4] + A[5] + A[6] = 5.
After that, there will be three ropes whose lengths are greater than or equal to K = 4. It is not possible to produce four such ropes.

Write a function:

def solution(K, A)

that, given an integer K and a non-empty array A of N integers, returns the maximum number of ropes of length greater than or equal to K that can be created.

For example, given K = 4 and array A such that:

A[0] = 1
A[1] = 2
A[2] = 3
A[3] = 4
A[4] = 1
A[5] = 1
A[6] = 3
the function should return 3, as explained above.

Write an efficient algorithm for the following assumptions:

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


Решение:

def solution(K,A):

      ropes = 0
      count = 0

      for i in range(len(A)):
            if A[i] >= K:
                    ropes +=1
                    count = 0
            else:
                count += A[i]

                 if count >= K:
                        ropes +=1
                        count = 0


       return ropes

Tags: кодилити, программирование, учеба
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    Бешеное что-то творится с рынком труда для разработчиков. Сегодня пришло предложение (одно из многих), которое позволит мне самолично погасить всю…

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