Greedily take Cow as long as you can.

Just print all index $$$A[i*K][j*K]$$$

Prefix Sum

Bruteforce works, now analyse why it works.

Sum of Harmonic series

Count no of substrings with equal 0s and 1s

Replace all 0 with -1. Now all segments with equal 0 and 1 have zero sum.

Instead of counting segments inside each range. For each substring with zero sum, count segments it is a part of.

Greedy, always take the index with maximum value of $$$A-i$$$

Binary search FTW

Binary search on the value you will add in $$$k^{th}$$$ operation.

Delete one road, now path between any pair of friends is unique. Try to count paths which do not lie between any pair of friends.

Given an array A, and multiple queries $$$L_i$$$ and $$$R_i$$$. Can you find the minimum value in this range, and how many times it appears?