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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Maze generating algorithm in grid

What is the best algorithm to generate a maze in a grid? I have heard of Kruskal's algorithm and the recursive backtracker amongst other but both of these rely on walls.What would be the best algorithm to create amaze where one entire cell is a…
user2592835
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recursive Permutation of a 3 Digit Number

I am working on finding All permutations of a 3-Digit Number recursively. I am tired with making up the following permutation Method: static int a = 1; static int b = 2; static int c = 3; static int aCount; static int bCount; …
Obzajd
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Backtracking Python script to find multiple solutions of "Clouds" puzzle

Clouds puzzles have the following rules: Place some clouds into the grid. Clouds are in the shape of rectangles and squares, and at least two squares wide and two squares long. The clouds cannot touch each other, not even diagonally. The numbers…
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Python + Leetcode: Test cases are "leaking over"/"interfering" with each other for recursive problems/code solutions?

So I was working on Leetcode #39-Combination Sum . And my test cases appear to be "leaking over/interfering" (best choice of words I could come up with) with each other: For example, when I run the first test case (candidates = [2,3,6,7]; target =…
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How to convert the following backtracking code into a top down head recursive memoized version?

I am trying to solve the famous Coin Change problem, below is the problem statement!! Coin Change II You are given an integer array coins representing coins of different denominations and an integer amount representing a total amount of…
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Understanding the for loop in Python permutation algorithm (Back-Tracking)

I'm currently working on a permutation algorithm in Python, and I'm having trouble understanding how the for loop inside the backtrack function works. I would appreciate it if someone could provide a clear explanation of its behaviour. Here's the…
user21055738
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How to find multiple Soduko solutions instead of one using backtracking?

I'm implementing a backtracking algorithm using Java to find a solution to a given Soduko board. I'm trying to modify the algorithm to instead give all possible solutions, however the modified algorithm is not working. See details below: public…
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ReDoS-resistant regex for removing whitespaces around a comma

I have a regex in Java that matches zero or more whitespace characters, followed by a comma, followed by zero or more whitespace characters. To clean up the Strings I use the following: String new1 = test1.replaceAll("\\s*,\\s*", ","); If I…
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C# complex goal function optimization problem

I encountered the following problem today: I have to sort items into slots, based on sizes, so that the slots are most full. If multiple solutions exist to this, then I have to take into account the achieved priority score of the sort. (So there are…
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Recursion to Iteration: How to implement a statement after recursive call in iterations?

I am currently working on a program that takes items from a list recursively and uses them. My problem now is: After the recursive call, the item is added back to the list. My codes looks about as follows (except there ist other stuff going on but…
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Can someone please explain me the backtracking of this recursion, I don't know why but it is adding current vector to ans vector 2 times

#include #include using namespace std; void getAns(char s, vector current, vector> &ans, int n, int i){ if (i >= n) { ans.push_back(current); return; } if (s == 'M'){ …
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Finding the longest palindrome in a single-dimensional array, using recursion, without loops, in Java

The details of the problem are as the same as described in title. The time complexity and space complexity can be ignored in the specific question. I did not stumble upon questions involving palindromes in my studies, so I am not at all sure about…
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How to find all possible paths from one rdf node to another? Any optimization on backtracking search?

In KG we have sample Rdf triples be like. input1 <---- f(x) -----> ouput1 <----- f(x) -----> output2 <----- f(x) -----> output3 My goal is to find all posibble paths from Input1 - output3. we start from (Input1) and everytime we will try to find…
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Why is this path update in DFS correct?

I don’t understand why the paths printed here would be correct. How does the path parameter not permanently get changed after child nodes are added to the path here? For example, say I have a graph like 1 with child nodes 2 3, where 2 has child…
Kashif
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Understanding solution to the Optimal Account Balancing (Leetcode 465) in python

The problem can be accessed from this link https://leetcode.com/problems/optimal-account-balancing/ *** Didn't realize this was only accessible by premium members, here is the problem statement and examples*** You are given an array of transactions…