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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how is this code working? backtracking and recursion

This is a working code that solves the sudoku: def is_valid(board, row, col, num): for i in range(9): if board[row][i] == num: return False for i in range(9): if board[i][col] == num: return False …
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Least number of coins needed using a Hash Map (Timing Out)

I'm writing a function to find the least number of coins required to make a certain amount of change. See this problem This is a Dynamic Programming problem, however, instead of using a traditional array I am trying to use an Object to memoize the…
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Recursion : Print all longest common subsequence

Iam trying to print all possible longest common subsequence using below code 1-Firstly i found LCS length dp matrix and trying using recursion to produce all possible outputs. ################################################Print ALL LCS…
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Why would you use Trie data structure in WordSearch problem given below?

Given an m x n board of characters and a list of strings words, return all words on the board. Each word must be constructed from letters of sequentially adjacent cells, where adjacent cells are horizontally or vertically neighboring. The same…
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Subset (PowerSet) of an array not producing the correct output

I am working on a problem where I have to find all the possible subsets (powerSet) of an array. I am using Recursive backtracking for this. I was playing with the solution to get a feel for how the recursive calls are connected. I am having trouble…
h_a
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Backtracking Problem or other better solution to find a sum from array

I think this is backtracking problem but I just can't convert my thought to code. So sample working code will be appreciated. There might be other way to solve this, which I'd like to know too. Given an array with N element. Divide into 3 separate…
Harts
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cant store the value in global variable

Im trying to do permutation problem in leetcode with backtracking Algorithm, While Printing I got all the Possiblities but when i Trying to store those value in global variable I'm not allow to…
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Knight walk backtracking solution issue

I have a doubt on the backtracking solution I wrote for below problem: Given a square chessboard of N x N size, the position of Knight and the position of a target are given. We need to find out the minimum steps a Knight will take to reach the…
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Solving TweetMazes with Recursive Backtracking in Python - Debug help request

I've been teaching myself Python as first steps in seeing if I want to totally change careers from teaching into some kind of software development. So far it's been going well, and I've been working on small projects to really stretch my abilities.…
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Solving a Sudoku field with Recursion and Backtracking in C

My challenge is to solve a given Sudoku field with recursion and Backtracking. We already do have some code, but we do not know how to implement the Backtracking. Here is our Code: int solve( int row, int col ) { if (getValueFromField(row, col)…
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Why my method of leetcode recursive backtracking is wrong for using such parameter?

I was trying to solve Leetcode JumpGame using a recursive backtracking problem by the following method. It is wrong, but my answer is just one variable name different than the solution. I used "position" instead of "nextPosition" in the recursion.…
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Algorithm for Lights-Out Game without Toggling

I have a problem much like the Lights Out game (Lights out game algorithm) but without toggling the lights. I have an n-by-n grid. When I "activate" a tile in the grid, the activated tile and its adjacent (4, except on the sides of the grid, of…
Eric Cochran
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Backtracking prorblem and I don't know if my plan to solve it is correct

I am practicing a backtracking problem and here is the problem description: https://practiceit.cs.washington.edu/problem/view/cs2/sections/recursivebacktracking/travel Write a method travel that accepts integers x and y as parameters and uses…
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An erroneous successful parsing in a recursive descent parser

I have the following code. It's a recursive descent parser with backtracking. /*\ /*\ |*|--------------|*| |*| Grammar: |*| |*| A -> ( A ) B |*| |*| | [ A ] B |*| |*| | n B |*| |*| | B |*| |*| |*| |*|…
Aphrontos
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How to add multiple solution with bactraking method

I'm trying to learn bactracking however, while I would like to add all solution to my arraylist, it only contains the first solution that my method found. I checked isSafe method, it is correct. the only problem is my queensList method. could you…