Segment Tree Test

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Points: 15 (partial)
Time limit: 0.5s
Java 1.0s
Python 2.5s
Memory limit: 16M
Python 256M

Problem type

Xyene is doing a contest. He comes across the following problem:

You have an array of elements, indexed from to . There are operations you need to perform on it.

Each operation is one of the following:

• C x v Change the -th element of the array to .
• M l r Output the minimum of all the elements from the -th to the -th index, inclusive.
• G l r Output the greatest common divisor of all the elements from the -th to the -th index, inclusive.
• Q l r Let be the result of the operation G l r right now. Output the number of elements from the -th to the -th index, inclusive, that are equal to .

At any time, every element in the array is between and (inclusive).

Xyene knows that one fast solution uses a Segment Tree. He practices that data structure every day, but still somehow manages to get it wrong. Will you show him a working example?

Input Specification

The first line has and .

The second line has integers, the original array.

The next lines each contain an operation in the format described above.

Output Specification

For each M, G, or Q operation, output the answer on its own line.

Sample Input 1

5 5
1 1 4 2 8
C 2 16
M 2 4
G 2 3
C 2 1
Q 1 5

Sample Output 1

2
4
2

Sample Input 2

5 2
1 1 2 2 2
Q 1 4
Q 3 5

Sample Output 2

2
3

• commented on Feb. 4, 2021, 7:52 p.m.

https://dmoj.ca/submission/1143175 has some interesting variable names....

• commented on Nov. 21, 2020, 3:06 a.m.

How big is case 15? Why must we optimize our code so much?

• commented on Nov. 21, 2020, 3:38 a.m. edited

My solution using a recursive segment tree with no constant optimizations passes in 1.370s in the worst case.

My hint for you is to answer all queries using a segment tree: std::unordered_map is extremely slow.

• commented on Nov. 21, 2020, 10:29 p.m.

Oh I thought it was always constant time.

• commented on Sept. 11, 2021, 6:46 p.m. edited

I think accessing an unordered_map key is but it has a really bad constant factor. I could be wrong but believe it is almost as slow as .

• commented on Oct. 31, 2019, 12:04 p.m. edited

My solution is but is getting TLE verdict from Case 12 onward. Any tips to optimize?

• commented on Oct. 31, 2019, 2:42 p.m.

iam not sure , but may try iterative segment tree (not sure if it's feasible to implement it easily) , also try unordered map or any optimised map for 4th query

• commented on Dec. 8, 2020, 9:49 p.m.

I tried using iterative segtree but it's still too slow: https://dmoj.ca/submission/3191595

• commented on Dec. 9, 2020, 1:44 a.m.

Ruby won't work here unfortunately, its about as fast as CPython.

• commented on Nov. 23, 2020, 8:16 p.m.

Apparently unordered map is too slow.