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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All possible N-Queens

The classic N-Queens problem finds a way to place n queens on an n×n chessboard such that no two queens attack each other. This is my solution to the N-Queens problem. class Solution(object): def solveNQueens(self, n): """ :type…
Melissa Stewart
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How to transfer an outside recursion program into a non-recursive form (using stack not CPS)?

there are many questions about how to convert recursive to non-recursive, and I also can convert some recursive programs to non-recursive form note: I use an generalized way (user defined Stack), because I think it is easy to understand, and I use…
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How does this recursive-backtrack solution work for solving arithmetic-expression?

I am trying to solve this arithmetic expression problem where I take n (here 5) elements in an array and try all combination of operators in (+ - *) to find if the expression is divisible by 101 Here, we are not concerned with order of…
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Unable to track why string permutations are not being appended in a global variable for array permutations

I am trying to code the String permutation problem. Instead of string I have a list of integers like [1,2,3]. I have to print out all possible permutations of the list. However, there's some issue with my code that I'm not able to figure out.…
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Golang sudoku algorithm not working

I'm very new to Golang, I'm trying to do a sudoku with backtracking algorithm. But when I run my program, there are no errors but it only displays the grid not complete, with empty cases here is my code : package main import "fmt" var sudoku =…
Sam Caneau
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Modify Knight's Tour Algorithm to Print All Solutions

I recently pulled a C program (https://repl.it/Klpv) that searches for a knight's tour on an 8 by 8 board. I re-wrote the program in JavaScript (since I understand JS better), then I modified the program so that is can search for a solution on any…
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Fixed values not repeated over column and row

I want to create a matrix in R with a set number of variables (e.g. 1 to 10). Those variables should be randomly assigned over rows and columns BUT should not be repeated in either (so number 1 should be once in row 1 and once in column 1)! So for…
shampoo
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Keeping track of path through a maze

The program is using backtracking to find out a way out of the maze(which it does fine). The problem occurs when I try to print out the correct path I took. This is my solveMaze() method. boolean result = false; …
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Connected recursive calls

I am trying to solve a puzzle where I have broken it down into 2 separate problems that both require recursion. When the 1st recursive problem is solved I want to then call the next recursive problem and when that is solved the puzzle is then…
Scot
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longest common subsequence java (recursive)

The problem I'm working on is here: http://practiceit.cs.washington.edu/problem/view/cs2/sections/recursivebacktracking/longestCommonSubsequence basically we are given two strings and we are requested to find the longest common subsequence. I've…
Amber
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How to organize elements (pieces of Tetris) recursively

I'm learning recursion but I need a reference on how to start making the algorithm. I need to organize blocks to use all the pieces, with the max possible fill of the board. Thanks to all.
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How to solve Sudoku by backtracking and recursion?

the reason why I am creating this new thread instead of just reading the answers to this particular question that have been given before is that I feel I just don't fully understand the whole idea behind it. I can't seem to get my head around the…
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Backtracking maze solver in C

I am writing the find path solution for maze [30][30] I used backtracking in path find function; Here is pseudo code: bool find_path(myMap,myVisited,myPath,v,h) find starting point [v,h] then run find_path function for that point mark the room as…
Taylor
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Java - Complex Recursive Backtracking

For Java practice I started working on a method countBinary that accepts an integer n as a parameter that prints all binary numbers that have n digits in ascending order, printing each value on a separate line. Assuming n is non-negative and…
Trafton
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Using recursive backtracking on a randomly generated maze

I've been programming for about five years now and I had no trouble creating a dynamic maze. But now that it comes to recursive backtracking I have absolutely no idea where to start. I've read a lot of tutorials, topics and some algorhytm wiki's…