What is backtracking?

Backtracking is a general algorithmic technique for solving problems recursively by trying to build a solution incrementally. It removes solutions that fail to satisfy the constraints of the problem at any point in time (i.e., it 'backtracks').

How can I identify a problem that can be solved with backtracking?

Problems that ask for all possible solutions (e.g., all permutations, all combinations, all paths) or for a single valid solution in a large search space (e.g., Sudoku, N-Queens) are often good candidates for a backtracking approach.

Recursive Algorithms

Backtracking Interview Questions

Explore the search space of problems like permutations, combinations, and Sudoku with backtracking. Our guide provides a template and AI-powered hints to master this key technique.

Generating All Subsets

Backtracking is a methodical way of trying out different sequences of decisions, and undoing them if they don't lead to a solution. It's perfect for problems that require exploring all possible configurations.

                            function subsets(nums) {
                            const result = [];
                            function backtrack(start, currentSubset) {
                            result.push([...currentSubset]);
                            for (let i = start; i < nums.length; i++) {
                            currentSubset.push(nums[i]);
                            backtrack(i + 1, currentSubset);
                            currentSubset.pop(); // Backtrack
                            }
                            }
                            backtrack(0, []);
                            return result;
                            }
                        

AI Coach Hint: The core of any backtracking solution is the 'choose, explore, unchoose' pattern. In this example: `currentSubset.push()` is choose, `backtrack()` is explore, and `currentSubset.pop()` is unchoose. This pattern is applicable to a wide variety of backtracking problems.