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.

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Time and Space Complexity for Leet Code Problem 39: Combination Sum

I was practicing backtracking problems and started off with the Combination Sum problem in Leetcode 39. I worked on my own solution after watching a few YouTube videos to understand the problem better since my solution was failing even though I felt…
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Cannot assign variables inside backtracking base condition

I want to implement a backtrack algorithm to find a minimum hamiltonian path, but I ran into a question: why I cannot assign a variable to a value inside the "if" in the code below? cycle = [0] start = 0 visited = set() num_nodes =…
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What is the logical error for this Python program to generate all possible unique ways to represent n=3 as sum of positive integers?

Python program to generate all possible unique ways to represent n=3 as sum of positive integers: def fun(): res=[] a=[] def backtracking(n): if(n==0): res.append(a) print(res) return …
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What is time and space complexity of rat in maze backtracking problem I am confused

I am solving a problem where we need to make code by which rat can start from a point reach the destination point . Here 0 means block path, 1 means open path. rat can move 4 different sides(down,left,right,up). I understand concept and I understand…
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Unable to understand the recursion tree for the problem, printing all permutations of a given string

This is with respect to the problem, printing all permutations of a given string ABC. As far as I have understood, the program first prints ABC, then the string gets reset to ABC (which is the same as the first permutation of the string in this…
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why it grid become zero after one travers

In a gold mine grid of size m x n, each cell in this mine has an integer representing the amount of gold in that cell, 0 if it is empty. Return the maximum amount of gold you can collect under the conditions: Every time you are located in a cell you…
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How would this shell-sort algorithm be coded in recursive?

I understand that any iterative function can be written recursively, but I still don't quite understand how to write it as a recursive function. This function receives an array (elements) and a int (number of elements), and sorts them from lower to…
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Cant we use memoization with backtracking?

In todays LeetCode challenge, (LeetCode Problem L-1293, My first idea was to go with backtracking, and then use memoization to make it qudratic or cubic from exponential. But, the dp gave wrong ans while the recursion gave the right one. After…
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How can I implement recursive backtracking for this sudoku solver without using any for loops?

I am trying to create a sudoku solver that uses recursive backtracking, however, I am not using any for loops in my program. This makes it difficult since when using the backtracking method, I need to use a for loop to iterate through the guesses…
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Maximum recursion depth exceeded when generating a maze in python with recursive backtracking

I made a program that ask the user a size and generate a perfect maze of size n^2 using the recursive backtarcking algorithm. I've run into this error and saw that i could simply use : sys.setrecursionlimit(8000) It worked well at the begining but…
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Need help "Sudoku Solver Backtracking" Java

I'm having trouble writing a Backtracking algorithm (Sudoku Solver) for my Sudoku project. My idea is to create a 2D array variable "initial" as an initializer array to push into the player's interface and use the "initial" variable to pass in the…
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Why the array returned by the combinationSum function is empty (Javascript)?

The resultArr returned by the combinationSum function is empty. When I console log the ds array, it prints the correct answer, but the final output array is [[],[]]. var combinationSum = function(candidates, target) { const resultArr = [] …
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Getting unknown error in SudokuSolver Backtracking problem

I was trying a Backtracking problem (SudokuSolver) I am getting an error which no-one could resolve or even understand. Hence I am seeking help here. The problem is as follows: And the main function/part of my code is: Here my removerow, removecol…
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Having difficulty identifying the next step compiler will take after a recursive call

I am having difficulty understanding this code. class Solution { public List> subsets(int[] nums) { List> subsets = new ArrayList<>(); generateSubsets(0, nums, new ArrayList(), subsets); …
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Backtracking problem in Knights tour algorithm

**Edit: I managed to find solution for my problem so i put the correct code in place. Everything works perfect now. I'm trying to complete the last stage of a project in Jetbrains Academy but I can't make my approach to the problem work: It gives…