Leetcode 2698. Find the Punishment Number of an Integer

Sum the squares i^2 for all i in [1..n] such that the decimal digits of i^2 can be partitioned into contiguous substrings whose integer values add up to i. This is solved by testing each i with a DFS/backtracking over digit partitions (n ≤ 1000, i^2 has at most a few digits so pruning suffices).