Codility - Lesson 2 Arrays

Source Link:
https://codility.com/programmers/lessons/2-arrays/

Some Notes:
Array is a data-structure that can be used to store many items in one place.

2.4. Iterating over an array

Knowing that the array contains of N elements, we can iterate over consecutive integers from index 0 to index N −1.

2.6. Exercise

Problem: Given array A consisting of N integers, return the reversed array.

Solution: We can iterate over the first half of the array and exchange the elements with those in the second part of the array.

Reversing an array.
1 def reverse(A):
2 N = len(A)
3 for i in xrange(N // 2):      // i from first to last until N/2 <--- important
4 k = N - i - 1                      // k from last to first until N/2 (let k = N-i-1)
5 A[i], A[k] = A[k], A[i]    // then, swap A[i] A[k]
6 return A                           // reverse the array