Buggy python submission (verdict: Time Limit Exceeded):
n = int(input())
a = [int(i) for i in input().split()]
 
a_dict = {}
for v in a:
    if v in a_dict:
        a_dict[v] += 1
    else:
        a_dict[v] = 1
 
 
if n % 2 == 0:
    possible_list = [i for i in range(1, n, 2)]
    for k, v in a_dict.items():
        if v != 2 or k not in possible_list:
            print(0)
            exit()
else:
    possible_list = [i for i in range(0, n, 2)]
    if a_dict[0] != 1:
        print(0)
        exit()
    else:
        a_dict[0] = 2
        for k, v in a_dict.items():
            if v != 2 or k not in possible_list:
                print(0)
                exit()
 
print(2 ** (n // 2) % (10 ** 9 + 7))


Fixed submission:
n = int(input())
a = [int(i) for i in input().split()]

a_dict = {}
for v in a:
    if v in a_dict:
        a_dict[v] += 1
    else:
        a_dict[v] = 1

 
if n % 2 == 0:
    possible_list = {i: True for i in range(1, n, 2)}
    for k, v in a_dict.items():
        if v != 2 or k not in possible_list:
            print(0)
            exit()
else:
    possible_list = {i: True for i in range(0, n, 2)}
    if a_dict[0] != 1:
        print(0)
        exit()
    else:
        a_dict[0] = 2
        for k, v in a_dict.items():
            if v != 2 or k not in possible_list:
                print(0)
                exit()
 
print(2 ** (n // 2) % (10 ** 9 + 7))

Buggy python submission (verdict: Runtime Error):
n = int(input())
a = [int(i) for i in input().split()]

# aの各数値の個数をdictで保持(数値:個数) 
a_dict = {}
for v in a:
    if v in a_dict:
        a_dict[v] += 1
    else:
        a_dict[v] = 1

# a_dictの中になければならない数値のリストを作成
possible_list = {i: True for i in range(1, n, 2)}
 
can = True
if n % 2 == 0:
    for k, v in a_dict.items():
        # 数値が2個でない、もしくはkがpossible_list内に存在しないならFalse
        if v != 2 or k not in possible_list:
            can = False
            break
else:
　　　　if a_dict[0] != 1:
        can = Falsen = int(input())
a = [int(i) for i in input().split()]

# aの各数値の個数をdictで保持(数値:個数) 
a_dict = {}
for v in a:
    if v in a_dict:
        a_dict[v] += 1
    else:
        a_dict[v] = 1

# a_dictの中になければならない数値のリストを作成(0以外)
 
if n % 2 == 0:
    possible_list = {i: True for i in range(1, n, 2)}
    for k, v in a_dict.items():
        # 2個でない、もしくはpossible_list内に存在しない数値ならFalse
        if v != 2 or k not in possible_list:
            print(0)
            exit()
else:
    possible_list = {i: True for i in range(0, n, 2)}
    if a_dict[0] != 1:
        print(0)
        exit()
    else:
        a_dict[0] = 2
        for k, v in a_dict.items():
            if v != 2 or k not in possible_list:
                print(0)
                exit()
 
print(2 ** (n // 2) % (10 ** 9 + 7))
    else:
        for k, v in a_dict.items():
            if v != 2 or k not in possible_list:
                can = False
                break
 
if can:
    print(2 ** (n // 2) % (10 ** 9 + 7))
else:
    print(0)

Fixed submission:
n = int(input())
a = [int(i) for i in input().split()]

a_dict = {}
for v in a:
    if v in a_dict:
        a_dict[v] += 1
    else:
        a_dict[v] = 1

 
if n % 2 == 0:
    possible_list = {i: True for i in range(1, n, 2)}
    for k, v in a_dict.items():
        if v != 2 or k not in possible_list:
            print(0)
            exit()
else:
    possible_list = {i: True for i in range(0, n, 2)}
    if a_dict[0] != 1:
        print(0)
        exit()
    else:
        a_dict[0] = 2
        for k, v in a_dict.items():
            if v != 2 or k not in possible_list:
                print(0)
                exit()
 
print(2 ** (n // 2) % (10 ** 9 + 7))

Buggy python submission (verdict: Runtime Error):
n = int(input())
a = [int(i) for i in input().split()]

# aの各数値の個数をdictで保持(数値:個数) 
a_dict = {}
for v in a:
    if v in a_dict:
        a_dict[v] += 1
    else:
        a_dict[v] = 1

# a_dictの中になければならない数値のリストを作成
possible_list = {i: True for i in range(1, n, 2)}
 
can = True
if n % 2 == 0:
    for k, v in a_dict.items():
        # 数値が2個でない、もしくはkがpossible_list内に存在しないならFalse
        if v != 2 or k not in possible_list:
            can = False
            break
else:
　　　　if a_dict[0] != 1:
        can = False
    else:
        for k, v in a_dict.items():
            if v != 2 or k not in possible_list:
                can = False
                break
 
if can:
    print(2 ** (n // 2) % (10 ** 9 + 7))
else:
    print(0)

Fixed submission:
n = int(input())
a = [int(i) for i in input().split()]

a_dict = {}
for v in a:
    if v in a_dict:
        a_dict[v] += 1
    else:
        a_dict[v] = 1

 
if n % 2 == 0:
    possible_list = {i: True for i in range(1, n, 2)}
    for k, v in a_dict.items():
        if v != 2 or k not in possible_list:
            print(0)
            exit()
else:
    possible_list = {i: True for i in range(0, n, 2)}
    if a_dict[0] != 1:
        print(0)
        exit()
    else:
        a_dict[0] = 2
        for k, v in a_dict.items():
            if v != 2 or k not in possible_list:
                print(0)
                exit()
 
print(2 ** (n // 2) % (10 ** 9 + 7))

Buggy python submission (verdict: Time Limit Exceeded):
n = int(input())
a_list = list(map(int, input().split()))

for i in range(1, n, 2):
    if a_list.count(n - i) != 2:
        print(0)
        exit()

if n % 2 != 0:
    if a_list.count(0) != 1:
        print(0)
        exit()
    else:
        print((2 ** -(-(len(a_list) - 1) // 2)) % (1000000000 + 7))
else:
    print((2 ** (len(a_list) // 2)) % (1000000000 + 7))


Fixed submission:
n = int(input())
a = [int(i) for i in input().split()]

a_dict = {}
for v in a:
    if v in a_dict:
        a_dict[v] += 1
    else:
        a_dict[v] = 1

 
if n % 2 == 0:
    possible_list = {i: True for i in range(1, n, 2)}
    for k, v in a_dict.items():
        if v != 2 or k not in possible_list:
            print(0)
            exit()
else:
    possible_list = {i: True for i in range(0, n, 2)}
    if a_dict[0] != 1:
        print(0)
        exit()
    else:
        a_dict[0] = 2
        for k, v in a_dict.items():
            if v != 2 or k not in possible_list:
                print(0)
                exit()
 
print(2 ** (n // 2) % (10 ** 9 + 7))

Buggy python submission (verdict: Time Limit Exceeded):
n = int(input())
a_list = list(map(int, input().split()))

for i in range(1, n, 2):
    if a_list.count(n - i) != 2:
        print(0)
        exit()

if n % 2 != 0:
    if a_list.count(0) != 1:
        print(0)
        exit()
    else:
        print(2 ** -(-(len(a_list) - 1) // 2))
else:
    print(2 ** (len(a_list) // 2))

Fixed submission:
n = int(input())
a = [int(i) for i in input().split()]

a_dict = {}
for v in a:
    if v in a_dict:
        a_dict[v] += 1
    else:
        a_dict[v] = 1

 
if n % 2 == 0:
    possible_list = {i: True for i in range(1, n, 2)}
    for k, v in a_dict.items():
        if v != 2 or k not in possible_list:
            print(0)
            exit()
else:
    possible_list = {i: True for i in range(0, n, 2)}
    if a_dict[0] != 1:
        print(0)
        exit()
    else:
        a_dict[0] = 2
        for k, v in a_dict.items():
            if v != 2 or k not in possible_list:
                print(0)
                exit()
 
print(2 ** (n // 2) % (10 ** 9 + 7))

Buggy python submission (verdict: Time Limit Exceeded):
n = int(input())
a_list = list(map(int, input().split()))
correct_list = []

for i in range(1, n, 2):
    correct_list.append(n - i)

for i in correct_list:
    if a_list.count(i) != 2:
        print(0)
        exit()

if n % 2 != 0:
    if a_list.count(0) != 1:
        print(0)
        exit()

print(2 ** len(correct_list))

Fixed submission:
n = int(input())
a = [int(i) for i in input().split()]

a_dict = {}
for v in a:
    if v in a_dict:
        a_dict[v] += 1
    else:
        a_dict[v] = 1

 
if n % 2 == 0:
    possible_list = {i: True for i in range(1, n, 2)}
    for k, v in a_dict.items():
        if v != 2 or k not in possible_list:
            print(0)
            exit()
else:
    possible_list = {i: True for i in range(0, n, 2)}
    if a_dict[0] != 1:
        print(0)
        exit()
    else:
        a_dict[0] = 2
        for k, v in a_dict.items():
            if v != 2 or k not in possible_list:
                print(0)
                exit()
 
print(2 ** (n // 2) % (10 ** 9 + 7))

Buggy python submission (verdict: Time Limit Exceeded):
n = int(input())
a_list = list(map(int, input().split()))

if n == 1:
    print(1)
    exit()

if n % 2 != 0:
    if a_list.count(0) != 1:
        print(0)
        exit()
    else:
        for i in range(2, n, 2):
            if a_list.count(i) != 2:
                print(0)
                exit()
            else:
                continue
    print(int(pow(2, (n - 1) / 2) % (pow(10, 9) + 7)))
else:
    for i in range(1, n, 2):
        if a_list.count(i) != 2:
            print(0)
            exit()
        else:
            continue
    print(int(pow(2, n / 2) % (pow(10, 9) + 7)))

Fixed submission:
n = int(input())
a = [int(i) for i in input().split()]

a_dict = {}
for v in a:
    if v in a_dict:
        a_dict[v] += 1
    else:
        a_dict[v] = 1

 
if n % 2 == 0:
    possible_list = {i: True for i in range(1, n, 2)}
    for k, v in a_dict.items():
        if v != 2 or k not in possible_list:
            print(0)
            exit()
else:
    possible_list = {i: True for i in range(0, n, 2)}
    if a_dict[0] != 1:
        print(0)
        exit()
    else:
        a_dict[0] = 2
        for k, v in a_dict.items():
            if v != 2 or k not in possible_list:
                print(0)
                exit()
 
print(2 ** (n // 2) % (10 ** 9 + 7))