Leetcode 1219. Path with Maximum Gold

Find the maximum sum of gold collectible by walking a path on an m x n grid that starts at any nonzero cell, moves up/down/left/right, cannot enter zero cells or revisit cells, and collects the gold from each visited cell. This is solved by exploring all simple paths via DFS/backtracking (feasible given m,n ≤ 15 and ≤ 25 gold-containing cells).