https://leetcode.com/problems/find-the-prefix-common-array-of-two-arrays/description/


A[..i] and B[..i] intersections sizes #medium #counting

https://leetcode.com/problems/first-completely-painted-row-or-column/description/


Index of first filled row/column in 2D matrix #medium #counting

https://leetcode.com/problems/tuple-with-same-product/description/


Count uniq 4-tupples a*b=c*d #medium #counting #sort

https://leetcode.com/problems/count-number-of-bad-pairs/description/


Count pairs a[i] - a[j] != j - i #medium #counting #sorting