编程题：一元多项式的加法运算

def read_polynomial():
poly = {}
while True:
exp, coeff = map(int, input().split())
if exp == -1 and coeff == -1:
break
poly[exp] = coeff
return poly
def add_polynomials(poly1, poly2):
result = {}
# Combine the keys from both polynomials
for exp in set(poly1.keys()).union(poly2.keys()):
# Sum the coefficients if they exist in both, else just take the existing one
result[exp] = poly1.get(exp, 0) + poly2.get(exp, 0)
return result
def format_polynomial(poly):
# Sort the terms by descending exponent
terms = sorted(poly.items(), reverse=True)
# Skip terms with a coefficient of 0
terms = [(exp, coeff) for exp, coeff in terms if coeff != 0]
# Format each term based on exponent and coefficient
result_terms = []
for exp, coeff in terms:
if exp == 0:
term = f"{coeff}"
else:
coeff_str = f"{coeff}" if abs(coeff) != 1 else '' if coeff ˃ 0 else '-'