def quadratic_congruence(a, b, c, p):
"""
Find the solutions to ``a x**2 + b x + c = 0 mod p
a : integer
b : integer
c : integer
p : positive integer
"""
from sympy.polys.galoistools import linear_congruence
a = as_int(a)
b = as_int(b)
c = as_int(c)
p = as_int(p)
a = a % p
b = b % p
c = c % p
if a == 0:
return linear_congruence(b, -c, p)
if p == 2:
roots = []
if c % 2 == 0:
roots.append(0)
if (a + b + c) % 2 == 0:
roots.append(1)
return roots
if isprime(p):
inv_a = mod_inverse(a, p)
b *= inv_a
c *= inv_a
if b % 2 == 1:
b = b + p
d = ((b * b) // 4 - c) % p
y = sqrt_mod(d, p, all_roots=True)
res = set()
for i in y:
res.add((i - b // 2) % p)
return sorted(res)
y = sqrt_mod(b * b - 4 * a * c, 4 * a * p, all_roots=True)
res = set()
for i in y:
root = linear_congruence(2 * a, i - b, 4 * a * p)
for j in root:
res.add(j % p)
return sorted(res)
def test_gf_csolve():
assert gf_value([1, 7, 2, 4], 11) == 2204
assert linear_congruence(4, 3, 5) == [2]
assert linear_congruence(0, 3, 5) == []
assert linear_congruence(6, 1, 4) == []
assert linear_congruence(0, 5, 5) == [0, 1, 2, 3, 4]
assert linear_congruence(3, 12, 15) == [4, 9, 14]
assert linear_congruence(6, 0, 18) == [0, 3, 6, 9, 12, 15]
# with power = 1
assert csolve_prime([1, 3, 2, 17], 7) == [3]
assert csolve_prime([1, 3, 1, 5], 5) == [0, 1]
assert csolve_prime([3, 6, 9, 3], 3) == [0, 1, 2]
# with power > 1
assert csolve_prime([1, 1, 223], 3, 4) == [4, 13, 22, 31, 40, 49, 58, 67, 76]
assert csolve_prime([3, 5, 2, 25], 5, 3) == [16, 50, 99]
assert csolve_prime([3, 2, 2, 49], 7, 3) == [147, 190, 234]
assert gf_csolve([1, 1, 7], 189) == [13, 49, 76, 112, 139, 175]
assert gf_csolve([1, 3, 4, 1, 30], 60) == [10, 30]
assert gf_csolve([1, 1, 7], 15) == []