题解 | 多项式输出

n = int(input())
a=list(input().split())

for i in range(n):
    if i == 0: # 第一项(默认不为0)
        if a[i] == '1': # 考虑系数1
             a[i] = f'x^{(n-i)}'
        elif a[i] == '-1': 
            a[i] = f'-x^{(n-i)}'
        else:
            a[i] += f'x^{(n-i)}'
    elif n-i == 1: # 一次项(考虑0,系数1，次数1)
        if a[i]=='0':
            a[i] = ''
        elif a[i] == '1':
            a[i] = f'+x'
        elif a[i] == '-1':
            a[i] = f'-x'
        elif int(a[i])>0:
            a[i] = f'+{a[i]}x'
        elif int(a[i])<0:
            a[i] = f'{a[i]}x'
    else: # 其他中间项(考虑0,系数1，次数1)
        if a[i]=='0':
            a[i] = ''
        elif a[i] == '1':
            a[i] = f'+x^{(n-i)}'
        elif a[i] == '-1':
            a[i] = f'-x^{(n-i)}'
        elif int(a[i])>0:
            a[i] = f'+{a[i]}x^{(n-i)}'
        elif int(a[i])<0:
            a[i] = f'{a[i]}x^{(n-i)}'
if a[n] == '0':
    a[n] =''
elif int(a[n]) > 0:
    a[n] = f'+{a[n]}'
print(''.join(a))