# Questions tagged [depth-first-search]

Depth-first search (DFS) is an algorithm for traversing or searching tree or graph data structures. One starts at the root (selecting some node as the root in the graph case) and explores as far as possible along each branch before backtracking.

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### Program that brute forces to find the minimum dominating set

This program solves the minimum dominating set but it takes an insanely long time to run. In case you do not know, in graph theory, a dominating set for a graph G is a subset D of its vertices, such ...
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### Finding the longest path on a grid with obstacles from the top to the bottom

I have a rectangle of . (platforms) and # (obstacles). I can start at any platform in the top row and go to the left, right or ...
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### Order of values in dfs and bfs

Let's consider a matrix of integers m: [[1,2,3] [4,5,6] [7,8,9]] Which represents a graph: ...
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### Backtracking graph algorithms for a word puzzle in Python

Motivation Recently, Buzzfeed released a browser-based puzzle game called "Pyramid Scheme." It is available at the following link. The puzzle in an initial state looks like this: To solve ...
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### Optimize Island Counter program

I am doing some assignments on my own and one of them is about a Island Counting program, I have come up with a working program but the problem is its very slow. When running test on for example maps ...
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### USACO Silver "Wormhole Sort" solver

I'm struggling a bit with a USACO silver question using python, http://usaco.org/index.php?page=viewproblem2&cpid=992. The question provides an unsorted list of numbers (cows) and a number of ...
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### Exceeded time limit on Trie search with Backtracking using Swift

I have been trying to solve Trie related problems over at leet code and came across this interesting problem 211. Design Add and Search Words Data Structure Here is the question for convenience: 211. ...
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### Shortest path in dags: Part 2/3 - the preprocessing and shortest path algorithms

Part 1/3 Part 3/3 I have this library for performing shortest path queries on dags (directed acyclic graphs). This post presents the shortest path algorithms and the topological sorters. Two ...
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Assuming I've the following code: ...
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### Find the shortest path from bottom left to top right in a maze using dfs and bfs algorithm

The following code is applying the depth-first search and breadth-first search algorithm to find the shortest path from bottom left to top right in a 10 x 10 grid. ...
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### Recursive DFS to find Euler Cycle

I have referred to this for what constitutes as an Euler Cycle: https://xlinux.nist.gov/dads/HTML/eulercycle.html This assignment required me to use Depth First Search and have the methods I have ...
1 vote
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### Helper get_all_neighbors (in a grid) function - python

So a little context to understand the code: This is a helper function to solve a bigger problem here Quick summary: A Knight is in a dungeon/2D grid of Ints, starts at 0,0 and must reach the last ...
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### Codewars: Path Finder

Task You are at position [0, 0] in maze NxN and you can only move in one of the four cardinal directions (i.e. North, East, South, West). Return true if you can reach position [N-1, N-1] or false ...
1 vote
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### Loan graph simplification in Java: the recursive DFS for searching for directed cycles

The class in this post returns a directed cycle in a financial loan graph. A financial loan graph consists of nodes and directed arcs. If there is an arc $(u, v)$ with weight $w = w(u, v)$, then ...
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### Find Passable Lanes in Rows and Columns

I have implemented the following question and looking forward for the reviews. Question Explanation : We have a two-dimensional board game involving snakes. The board has two types of squares on it: +...
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### Given a 2d matrix with chars find the target string

I am looking for a simpler implementation of the following question. Could it get better? I am expecting the new solution via DFS again. Thanks. OA: Given a 2d matrix with chars and a target string. ...
1 vote
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### How does one write DFS in python with a Deque without reversed for Trees?

I have implemented a correct version of DFS (with comments explaining the implementation): ...
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### Check if point is inside a bitmap shape

Inspired by this question, here's some C code to check if a point is "inside" of a shape on a simple black and white bitmap. For this exercise: Set bits form the "outlines" of a ...
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### C++ implementation of depth-first search

I got the C++ implementation of depth-first search (DFS) from here and made slight modifications to it. The modified code is as follows: ...
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### Detecting a cycle in a directed graph via an adjacency list implementation and a recursive DFS

Here's my attempt. I iterate through each vertex in the graph and do a DFS to see if I reach back on a vertex I already visited in this vertex's iteration. It seems to work but I am not satisfied with ...
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### LeetCode: Number of enclaves C#

https://leetcode.com/problems/number-of-enclaves/ Given a 2D array A, each cell is 0 (representing sea) or 1 (representing land) A move consists of walking from one land square 4-directionally to ...
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### Graph: Depth First Search (N citizens with pairs of friends)

I have solved problem 10608 on UVA Online Judge using Python 3.5.1. My solution works, but it takes too long to run when the online judge evaluates it. Problem There is a town with N citizens. It is ...
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### 01 Matrix is too slow when solved using DFS

I tried solving Leetcode 01 Matrix problem. It is running too slow when solved using DFS approach. Given a matrix consists of 0 and 1, find the distance of the nearest 0 for each cell. The distance ...
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### Depth First Search Using Stack in Python

I have implemented a depth first search using a stack (in a separate class). Any suggestions please on improvements for the below code: ...
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### Closest Pair heuristics, graph with adjacency matrix in C++17

I was trying to solve a problem that was briefly mentioned at the beginning of the "The Algorithm Design Manual" by Steven Skiena (Ch 1, Problem 26). It took me some time to build a working ...
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### LeetCode 839: Similar String Groups II

I'm posting my code for a LeetCode problem. If you'd like to review, please do so. Thank you for your time! Problem Two strings X and Y are similar if we can swap two letters (in different positions) ...
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### Sudoku solver using backtracting and depth-first-search

I've recently finished my first ever C program. I implemented a Sudoku solver that uses backtracking. Does my code look like a proper C-program? Are there any recommendations for improving my code? <...
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### Sum of all Paths in Binary Tree

Problem For the given binary tree return the list which has sum of every paths in a tree. i.e Every path from root to leaf. I've written following solution. ...
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### Kosaraju Algorithm in Java

Problem statement In simple words it say, count total Strongly connected components in the graph. All edges are undirected. I have the following code that uses ...
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### Recursive and iterative implementation on Kosaraju algorithm

Kosaraju algorithm is mainly phrased as two recursive subroutines running postorder DFS twice to mark SCCs with linear time complexity O(V+E) below, For each vertex $u$ of the graph, mark $u$ as ...
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### Depth First Search vs Breadth First Search

So after years of teaching myself, I think I'm ready to stand on the shoulders of giants and ask you a good question! I have a tree of nodes. What I want is a function that returns an array of the ...
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### GeeksForGeeks: Alien dictionary C#

https://www.geeksforgeeks.org/given-sorted-dictionary-find-precedence-characters/ please review for performance, the adjacency list is the problematic part for me. Given a sorted dictionary (array ...
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### LeetCode:MineSweeper C#

https://leetcode.com/problems/minesweeper/ please review for performance. I really don't like the implementation I made for GetNumberOfMines() function, but within the time limits i did this. it is ...
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### LeetCode: FloodFill C#

https://leetcode.com/problems/flood-fill/ An image is represented by a 2-D array of integers, each integer representing the pixel value of the image (from 0 to 65535). Given a coordinate (sr,...
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### N-Queens Puzzle

The N-Queens puzzle can be solved in many ways. One is by a depth-first-search backtracking algorithm. Below is my generalized version using mutual recursion: ...
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### LeetCode: Network Delay Time DFS solution C#

https://leetcode.com/problems/network-delay-time/ There are N network nodes, labelled 1 to N. Given times, a list of travel times as directed edges times[i] = (u, v, w), where u is the ...
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### algorithm to find a zero in a board game [closed]

I got asked this question in an interview and I came up with a solution which I shared in the below but apparently it was not enough to pass. I'm looking forward to hearing how this problem could be ...
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### Clojure depth first search maze problem from Classic CS Problems in Python Book

I am an experienced self-taught professional Python programmer working my way through the book Classic Computer Science Problems in Python to try to catch myself up on some of the things I missed by ...
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### Creating valid words on an n-by-n grid of characters using depth-first search

I am trying to create a word-finder game. There will be an n-by-n Board filled with Tiles. ...
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### A generic DFS in JavaScript

I implemented a general function for a depth-first-search (DFS) using JavaScript with default arguments and functions that need to be provided in order for it to work. This function is using ...
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### Find the lengths of strongly connected components in a graph

I wrote a code to calculate the lengths of strongly connected components in a graph. The results I get are correct but it scales horribly. This is the code I have. I understand that the runtime ...
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### LeetCode: critical connections in a network C# (Tarjan's algorithm)

https://leetcode.com/problems/critical-connections-in-a-network/ Please review for memory and runtime performance. There are n servers numbered from 0 to n-1 connected by undirected server-to-...
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### Optimize depth-first search for sliding tile puzzle

My current code implementing a depth-first search works well for puzzle 1. But my code is too slow; I think I use too many loops and I am not sure I am using the right data structure. So I have a ...
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### Maze path finder using Depth-First Search algorithm

I'm trying to resolve this kata from CodeWars. Kata exercise You are at position [0, 0] in maze NxN and you can only move in one of the four cardinal directions (i.e. North, East, South, West). ...
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### Javascript Tree Class 2

This question is the second version of the code here. I'm writing a general tree class. Specifically, each node should have oen parent, some number of children, and hold a value. I'm looking for ...
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### Javascript Tree Class

I got caught in the trap of implementing my own data structure. I've created a very general tree structure, where each node gets one parent, some children, and holds a value. I'm mostly looking for ...
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### Ruby implementation for Hacker Rank connected cells in a grid

https://www.hackerrank.com/challenges/connected-cell-in-a-grid/problem problem statement: Consider a matrix where each cell contains either a 1 or a 0. Any cell containing a 1 is called a ...
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