LITE - Light Switching
Farmer John tries to keep the cows sharp by letting them play with intellectual toys. One of the larger toys is the lights in the barn. Each of the N (2 <= N <= 100,000) cow stalls conveniently numbered 1..N has a colorful light above it.
At the beginning of the evening, all the lights are off. The cows control the lights with a set of N pushbutton switches that toggle the lights; pushing switch i changes the state of light i from off to on or from on to off.
The cows read and execute a list of M (1 <= M <= 100,000) operations expressed as one of two integers (0 <= operation <= 1).
The first kind of operation (denoted by a 0 command) includes two subsequent integers S_i and E_i (1 <= S_i <= E_i <= N) that indicate a starting switch and ending switch. They execute the operation by pushing each pushbutton from S_i through E_i inclusive exactly once.
The second kind of operation (denoted by a 1 command) asks the cows to count how many lights are on in the range given by two integers S_i and E_i (1 <= S_i <= E_i <= N) which specify the inclusive range in which the cows should count the number of lights that are on.
Help FJ ensure the cows are getting the correct answer by processing the list and producing the proper counts.
Line 1: Two space-separated integers: N and M
Lines 2..M+1: Each line represents an operation with three space-separated integers: operation, S_i, and E_i
Lines 1..number of queries: For each output query, print the count as an integer by itself on a single line.
0 1 2
0 2 4
1 2 3
0 2 4
1 1 4
if you not able to do then you watch the lecture of "code n code" on YOUTUBE
AC in one go and it is first segment tree problem in my coding life that i got ac in one go
spoj has a system to tell the verdict after processing all test cases. So you may be failing any of the 10 test cases, not a specific one
Great problem to start with segment tree lazy propagation
AC in 1 go.
naive algorithom with optimization got ac in one go
For the 10th case, try updating a segment that shares nodes that are both turned off and on. My error was assuming that if a whole segment was to be changed then there were only two possibilities: either the sum is 0 (because the segment is completely turned off) or the sum is the size of the segment (because the segment is completely turned on), then I realized there is an intermediate state: when you turn things on and off in the same segment, resulting in the difference between the size of the interval and the nodes that *will* be turned off. After fixing that I got acc :).Last edit: 2019-12-26 23:32:42
Last edit: 2019-11-23 15:45:10
AC in one go....But How to solve this without lazy propagation???