Zig Zag Sequence

HackerRank 問題: Zig Zag Sequence
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Question

In this challenge, the task is to debug the existing code to successfully execute all provided test files.

Given an array of n distinct integers, transform the array into a zig zag sequence by permuting the array elements. A sequence will be called a zig zag sequence if the first k elements in the sequence are in increasing order and the last k elements are in decreasing order, where k = (n+1)/2. You need to find the lexicographicall

Note: You can modify at most three lines in the given code. You cannot add or remove lines of code.

HackerRank 問題: Zig Zag Sequence

Answer

def findZigZagSequence(a, n):
    a.sort()
    # medium calculate fail without -1
    mid = int((n + 1)/2) - 1
    a[mid], a[n-1] = a[n-1], a[mid]

    st = mid + 1
    # end index offset wrong at first time
    ed = n - 2
    while(st <= ed):
        a[st], a[ed] = a[ed], a[st]
        st = st + 1
        # end index should be minus not plus
        ed = ed - 1

    for i in range (n):
        if i == n-1:
            print(a[i])
        else:
            print(a[i], end = ' ')
    return

test_cases = int(input())
for cs in range (test_cases):
    n = int(input())
    a = list(map(int, input().split()))
    findZigZagSequence(a, n)

Reference