My solution for this codejam problem: https://codejam.withgoogle.com/2018/challenges/00000000000000cb/dashboard/00000000000079cb

troublesort.py

def troublesort(V):
    done = False
    while not done:
        done = True
        for i in range(len(V)-2):
            if V[i] > V[i+2]:
                done = False
                V[i], V[i+2] = V[i+2], V[i]

def check(V):
    for i in range(len(V)-1):
        if V[i] > V[i+1]:
            return i
    return 'OK'


T = int(input())
for t in range(T):
    N = int(input())
    V = list(map(int, input().split()))
    troublesort(V)
    print("Case #{}: {}".format(t+1, check(V)))