# HDU 3397. Sequence operation

### Brief description:

… lxhgww got a sequence contains n characters which are all ‘0’s or ‘1’s. We have five operations here:

Change operations:

• 0 a b: change all characters into ‘0’s in [a, b]. (区间赋值
• 1 a b: change all characters into ‘1’s in [a, b]. (区间赋值
• 2 a b: change all ‘0’s into ‘1’s and change all ‘1’s into ‘0’s in [a, b]. (区间取反
Output operations:

• 3 a b: output the number of ‘1’s in [a, b].
• 4 a b: output the length of the longest continuous ‘1’ string in [a , b].