Module: Root decomposition


Problem

1 /6


Sum on segment - 1

Theory Click to read/hide

We have a problem about how to quickly calculate the sums on the interval l...r in a static array a in less than O(n) asymptotics.
Let's divide the array a into k blocks of the same size and first calculate the sum of elements for each of them.
Now, when answering the request, we can go through the elements of the array a and add them to the result, also if one of the blocks lies inside the segment, then we can add its sum to the result and skip the elements of this block.
The maximum number of operations per query with this algorithm is n / k + k, so the optimal k is equal to the square root of n.
 

Problem

Given an array a of length n (\(1 <= n <= 2 \cdot 10^6\)< /span>, \(1 <= a_i <= 10^9\)). Also given m (\(1 <= m <= 500\)) queries like l, r (\(1 <= l <= r <= n\)).

For each query, print the sum of numbers between l and r inclusive. Elements are numbered starting with 1 to n.

 

Examples
# Input Output
1
4
1 2 3 4
2
1 4
1 1
 10
1
2
5
5 5 5 5 5
1
5 5
 5

time 1000 ms
memory 256 Mb
Rules for program design and list of errors in automatic problem checking

Teacher commentary

Your Program

Attach a file with the source code of the program:

or select a programming language and type your program

Auto

       

Program check result To check the solution of the problem, you need to register or log in!