8 монет - 1 фальшивая

from random import shuffle
 
def scale(a1, a2):
    s1 = sum(a1)
    s2 = sum(a2)
    if s1 == s2:
        return None
    elif s1<s2:
        return 1
    return 2
    
a = [1]*7+[0]
shuffle(a)
print(a)
res1 = scale(a[:3], a[3:6])
if res1:
    k = res1-1
    res2 = scale([a[3*(res1-1)]], [a[3*res1-2]])
    if res2:
        print(3*res1 + res2 - 3)
    else:
        print(3*res1)
else:
    res2 = scale([a[6]], [a[7]])
    print(6 + res2)

from random import randint
#==============================================================================
def get_i_bad( lenn, arr, i_L, i_R, counter ):
    counter[0] += 1
    counter[:] = counter
    if ( L := sum( arr[i_L: i_L+lenn] ) ) < ( R :=  sum( arr[i_R: i_R+lenn] ) ):
        return i_L
    elif L > R:
        return i_R
#==============================================================================
def get_bad_1_from_bad_3( a, i_bad_3, counter ):
    i_bad_1 = get_i_bad(1, a, i_bad_3, i_bad_3 + 1, counter)
    if i_bad_1 != None:
        print(i_bad_1, counter[0])
    else:
        print(i_bad_3 + 2, counter[0])
#==============================================================================
def find_bad_ind(arr):
    counter = [0]
    i_L3    = 0
    i_R3    = 3
    i_bad_3 = get_i_bad( 3, a, i_L3, i_R3, counter )
    if i_bad_3 == None:
        i_bad_3 = 6
    get_bad_1_from_bad_3( a, i_bad_3, counter )
#==============================================================================
a = [1]*9
a[randint(0,8)] = 0
print(a)
find_bad_ind(a)

from random import shuffle
 
def scale(a1, a2):
    s1 = sum(a1)
    s2 = sum(a2)
    if s1 == s2:
        return 2
    elif s1<s2:
        return 0
    return 1
    
a = [1]*7+[0]
shuffle(a)
a += [0]
print(a)
 
res1 = scale(a[:3], a[3:6])
res2 = scale([a[res1*3]], [a[res1*3+1]])
print(res1*3 + res2 + 1)

from random import randint
#==============================================================================
def get_i_bad( arr, i_L, len_start, counter ):
    len_finish = len_start // 3
    i_C = i_L + len_finish
    i_R = i_C + len_finish
    res = None
    if ( L := sum( arr[i_L: i_L+len_finish] ) ) < ( R := sum( arr[i_R: i_R+len_finish] ) ):
        res = i_L
    elif L > R:
        res = i_R
    else:
        res = i_C
    return res, len_finish, counter+1
#==============================================================================
def find_bad_ind(arr):
    i_bad   = 0
    lenn    = len(arr)
    counter = 0
    while lenn > 1:
        i_bad, lenn, counter = get_i_bad( arr, i_bad, lenn, counter )
    print( i_bad, counter )
#==============================================================================
n            = 3 ** randint(0, 3)
a            = [1]*n
bad_ind      = randint(0, n-1)
a[ bad_ind ] = 0
print(f'n = {n}')
print(a)
print( bad_ind )
find_bad_ind(a)