I avoided backtracking for an embarrassingly long time. I had solved maybe 200 problems and could do graphs, DP, binary search, all of it. But the moment a problem wanted "all subsets" or "every valid arrangement," I went blank. I had memorized the subsets solution and the permutations solution as two separate spells, and when an interview asked for something slightly different, neither spell fit.
The thing that finally fixed it was not another solution. It was redrawing the problem.
Backtracking is DFS with an undo button
Here is the reframe that made everything click. A backtracking problem is a tree of decisions. The root is an empty candidate. Every edge is a choice you make. Every leaf is a finished candidate. Solving the problem means walking that tree depth-first, building a candidate as you descend and taking it apart as you climb back up.
That is the whole thing. Three steps, repeated:
