用for循环计算(1-3+5-7...99)的结果(两种方法)

1)
sum=0
count=1
for i in range(1,100,2):
    if count % 2==0:
        sum = sum - i
    else:
        sum = sum + i
    count = count+1
print(sum)

2)
sum = 0
count = 1
for i in range(1,100,2):
    sum = sum + i*count
    count = -count
print(sum)