[洛谷P1024]python一元三次方程求解

a, b, c, d = map(float, input().split())

def calEq(x):
    return a * x * x * x + b * x * x + c * x + d

# print(f"Input values: a={a}, b={b}, c={c}, d={d}")

ans = [0.00] * 3
loation  = 0

for i in range(-100, 101):
    left = i
    right = i + 1
    # 左端点是根
    if calEq(left) == 0:
        ans[loation] = left
        loation += 1
        # print("{:.2f}".format(left), end=' ')
    if calEq(left) * calEq(right) < 0:
        while right - left > 1e-3:
            mid = (left + right) / 2
            if calEq(mid) * calEq(right) > 0:
                right = mid
            else:
                left = mid
        ans[loation] = right
        loation += 1

for i in range(len(ans)):
    if i < len(ans) - 1:
        print("{:.2f}".format(ans[i]), end=' ')
    else:
        print("{:.2f}".format(ans[i]))

一开始用if elif，把right符合条件的跳过，出现问题，之后改用全if就AC了