Questions tagged [recursive-backtracking]

Recursive backtracking is a general algorithm for finding solutions to computational problems that incrementally builds partial solutions and drops those which are identified as futile *as early as possible*.

Recursive backtracking is a general algorithm for finding solutions to computational problems that incrementally builds partial solutions and drops as early as possible those partial solutions which are identified as futile i.e. such that can not lead to a correct solution.

It essentially involves building nested loops through recursion. Each loop embodies a series of choices. Each inner loop can accept a partial-solution-so-far and try its own choices in a loop, or reject the partial solution it is presented with, through early exit or an equivalent of the continue or break etc. statement.

The control is inverted in that the full solution is achieved in the innermost loop, which can act on it in a particular manner, like printing it to the output / external file, or calling a callback with the solution as an argument.

The backtracking computational structure is embodied in the states of the nested loops, in each of the nested loops' loop variables.

314 questions
1
vote
1 answer

How would I count the number of iterations of a Recursive Function in Python?

def solver(): empty_cell = empty_square() counter = 0 if not empty_cell: return True i,j = empty_cell[0],empty_cell[1] for num in range(1,10): counter += 1 if constraint_check(num,i,j): …
1
vote
0 answers

Maximum Product In Matrix

I was trying to calculate the maximum product that can be achieved when traveling from the top left of a 2D array to the bottom right. I know there is a solution here that uses dynamic programming in a bottom up manner (i.e. iterative for loops…
1
vote
0 answers

Backtracking to generate parentheses(Generating 3 pairs)

public List generateParenthesis(int n) { List list = new ArrayList<>(); backtrack(list,"",0,0,3); return list; } public void backtrack(List list, String str,int open, int close, int…
1
vote
1 answer

Why do we pop from the list at the end of each backtrack iteration?

I have a solution to the following problem: https://leetcode.com/problems/combinations/ List[List[int]]: def backtrack(first = 1, curr = []): # if the combination is done if len(curr) == k: …
user15740803
1
vote
2 answers

Print all possible combinations of r elements using string

I was trying to solve this question using this simple recursive and backtracking approach.My idea was this: code import java.util.*; public class Main { static void generate(String s, String ans , int r) { if(ans.length()-1==r) …
1
vote
1 answer

DFS Maze Solver returns false when correct

I'm currently working on a little maze solver project to get a better grasp of algorithms like depth-first search. It works in that turns the current position to 2, then checks one of the positions(up, down, left or right) if it's a 0(path) and it…
1
vote
3 answers

How does Recursive Backtracking work? Computerphile sodoku solver

I'm so confused by backtracking because when the recursive call returns, won't you replace the solution found by replacing the grid back to zero. So even if you find the solution would it not be erased because after calling the solve function you…
1
vote
1 answer

Backtracking - problem with list updates in the recurrsive call

I was trying to solve 797. All Paths From Source to Target from Leetcode. I thought of using Backtracking with recursion. In the below code, the list setOfPaths is also getting updated when I pop from path. I am not sure what I am doing wrong…
1
vote
0 answers

Backtracking recursive search function

Im having issues backtracking through a list of lists in order to solve the Skyscraper puzzle. My goal is to try an element, filter out the board after that element has been inserted , and check if the new board is valid, if it is , continue, if…
1
vote
3 answers

Multiply two numbers through recurssion

#include using namespace std; int multiply (int num1, int num2){ if (num1 > 0) return num2 + multiply(num1-1,num2); } int main(){ int mult = multiply(5,6); cout<
1
vote
1 answer

Recursive Backtracking no return value python

Full problem is on https://www.hackerrank.com/challenges/password-cracker/ I would like to know whats wrong with my recursive backtracking implementation Problem: Given an array of passwords, return "Wrong password" if word is not a combination of…
1
vote
0 answers

backtracking logical error with maze solving program

if i have a maze my code should see if i can walk on every free space (represented by dot '.') or not so i tried backtracking. the player can move in the four main directions but he can't choose the number of steps (he walks until he collides with…
1
vote
1 answer

JS Adding delay to a Sudoku backracker

I just finished implementing a backtracking algorithm which successfully solves a sudoku board. However, I would like to add delay so that it will be easier to visualize. Im assuming I need to use setTimeout() or setInterval(). I already tried…
1
vote
1 answer

Generate unique permutations from a multiset using backtracking and in lexicographic order

If there are duplicates (meaning our set is a multi-set), you can save considerable time and effort by avoiding identical permutations. For example, there are only ten distinct permutations of {1,1,2,2,2}, instead of 120. The…
1
vote
1 answer

8-queen problem How to show the placement on a board while The backtracking algorithm is working

I want to reporduce the placement on the board while the backtracking algorithm work. If I insert a Timeout, the ram of the tab fastly increase and crashes. How can i show the functionlity of the algorithm ? function solveNQUtil(board, col) { …