python day2

计算1-2+3-4.....99除了88以外所有数的和

sum = 0
i = 0
while i < 100:
    if i == 88:
        i += 1
        continue
    elif i % 2 == 0:
        sum = sum - i
    else:
        sum = sum + i
    i += 1
print(sum)

 进阶方法 带符号一起改变

i = 0
j = -1
sum = 0
while i < 100:
    i = i + 1
    if i == 88:
        continue
    else:
        j = -j
        sum = sum + i*j
print(sum)