Java代写：CSCI1933 Solving Grid Puzzles Using Stacks and Queues

发表于   |   分类于

通过实现Stack和Queue等基础数据结构，生成并求解迷宫类网格难题，涵盖递归回溯、路径搜索及Java图形可视化。

stack and queue

Overview

This document serves as a comprehensive technical exploration and instructional guide for a project in the University of Minnesota’s course CSCI1933. The project involves implementing and applying fundamental data structures—namely, Stacks and Queues—to generate and solve grid-based puzzles. This project offers practical exposure to recursive backtracking, pathfinding algorithms, and graphical visualization via Java GUI libraries.

The centerpiece of the project is the MyGrid.java class, where the primary logic for maze generation, visualization, and solving is implemented. The grid is structured as a two-dimensional array of cells, each with attributes that denote whether it has been visited, and whether walls exist to the right or below. Using stacks, the maze (grid) is constructed by simulating a depth-first search. Solving the maze uses a queue-based breadth-first search to find a path from the entrance to the exit.

Project Objectives

  • Develop proficiency with stack and queue data structures
  • Implement maze generation using randomized depth-first traversal
  • Solve the maze using breadth-first search with queue data structures
  • Visualize both the generated maze and the solution path using color-coded graphics
  • Practice good programming style, project organization, and documentation

Table of Contents

  1. Project Structure and Requirements
  2. Conceptual Foundation
  3. Provided Classes Overview

  4. Core Components

    • Grid Representation
    • Cell Attributes
    • Maze Generation (makeGrid)
    • Grid Visualization (drawGrid)
    • Maze Solving (solveGrid)
  5. Step-by-Step Implementation Guide
  6. Testing and Validation
  7. Best Practices and Coding Standards
  8. Conclusion

Project Structure and Requirements

To ensure compatibility with automatic grading scripts and maintain readability, submissions must follow these structural rules:

  • Submit a ZIP file named [partner1_x500]_[partner2_x500]_Project4.zip
  • The ZIP must contain a directory with the same name as the ZIP file

  • Inside the directory, include exactly two files:

    • MyGrid.java
    • README.txt

Code Constraints

  • Use only the following Java libraries: java.awt.Color, java.util.Random, java.util.Scanner
  • Do not use any external libraries, utility collections, or built-in stack/queue classes

README.txt Contents

  • Team members and x500s
  • Division of labor (if working with a partner)
  • Implementation assumptions
  • Extra features (if applicable)
  • Known bugs or limitations
  • References used during development

Style and Documentation Expectations

  • Meaningful comments that explain algorithmic choices
  • Clean, consistent indentation and formatting
  • Descriptive and appropriately concise variable names
  • Efficient algorithms with practical runtime performance

Conceptual Foundation

Before diving into implementation, it’s important to understand the fundamental structures and algorithms being used:

Stack

A stack is a Last-In-First-Out (LIFO) data structure. Elements are added to the top and removed from the top. In this project, stacks are used during maze generation to emulate a recursive depth-first search process.

Queue

A queue is a First-In-First-Out (FIFO) data structure. Elements are added to the rear and removed from the front. Queues enable breadth-first traversal of the grid during the pathfinding phase.

Grid

A grid (or maze) is composed of rectangular cells organized in rows and columns. The goal is to create a valid path from the entry point on the left side to the exit point on the right.

Provided Classes Overview

Several helper and structural classes are provided and must not be modified. Understanding their behavior is essential:

Cell.java

Each cell has:

  • visited (boolean): marks if the cell has been visited
  • right (boolean): true if a right wall exists
  • down (boolean): true if a bottom wall exists

Stack1Gen.java and Q1Gen.java

Custom implementations of:

  • Stack interface (Stack1Gen)
  • Queue interface (Q1Gen)
  • Node class (NGen) to support both data structures generically

Canvas.java and Square.java

Classes used to draw shapes to the screen.

  • Each cell is visualized using a colored square
  • Canvas is used to manage and display these squares graphically

Core Components

Grid Representation

1
2
3
Cell[][] grid;
int startRow;
int endRow;

The maze is stored in a 2D array of Cell objects. The grid dimensions depend on the difficulty level:

  • Level 1: 5x5
  • Level 2: 5x10
  • Level 3: 12x12

The entrance is on the left (grid[startRow][0]), and the exit is on the right (grid[endRow][cols-1]).

Cell Attributes

Each Cell has three main attributes:

  • visited: prevents revisiting the same cell
  • right: determines if a right-side wall exists
  • down: determines if a bottom wall exists

Maze Generation (makeGrid)

This static method creates and returns a new MyGrid instance. It uses a stack to implement a randomized depth-first search:

  1. Start at grid[startRow][0]
  2. Push current location onto the stack

  3. Loop while stack is not empty:

    • Peek the top of the stack
    • Randomly select an unvisited neighbor (up/down/left/right)
    • Remove the wall between current and neighbor
    • Mark neighbor as visited and push it
    • If no neighbors, pop the current cell

After generation, reset the visited attribute for all cells.

Grid Visualization (drawGrid)

This method uses Canvas and Square classes to display the grid:

  • Each cell is drawn as a colored square

  • Colors represent:

    • Unvisited cells
    • Visited cells (path)
    • Walls
    • Start and End points
  • Use cell.right and cell.down to determine which sides to draw walls on

Maze Solving (solveGrid)

This method uses a queue to implement breadth-first traversal:

  1. Initialize the queue with {startRow, 0}

  2. While the queue is not empty:

    • Dequeue a cell
    • If the cell is {endRow, cols-1}, exit
    • Mark it visited
    • Enqueue all reachable unvisited neighbors

Once solved, call drawGrid() again to visualize the path.

Step-by-Step Implementation Guide

Step 1: Implement Constructor

1
public MyGrid(int rows, int cols, int startRow, int endRow)
  • Create a rows x cols grid
  • Instantiate each cell: grid[i][j] = new Cell()
  • Assign startRow and endRow

Step 2: Implement makeGrid

  • Use a stack
  • Implement DFS with wall removal logic
  • Reset all visited flags after generation

Step 3: Implement drawGrid

  • Use loops to draw each row and column
  • Create square objects for each cell
  • Use Color class to apply appropriate color coding

Step 4: Implement solveGrid

  • Use a queue
  • Implement BFS traversal
  • At each step, check for exit cell
  • Update visited status
  • Call drawGrid after traversal completes

Step 5: Final Integration

  • Implement user interaction in main() (if applicable)
  • Test with all difficulty levels

Testing and Validation

Thoroughly test the implementation:

  • Grid generation should always produce a valid path from start to end
  • Solving algorithm should always find a path if it exists
  • Visual output should match expected structure

  • Ensure edge cases are handled:

    • Smallest grid (5x5)
    • Invalid inputs
    • Full wall scenarios

Best Practices and Coding Standards

  • Avoid magic numbers by defining constants
  • Break complex logic into helper methods (if allowed)
  • Use appropriate encapsulation and access modifiers
  • Clean up resources (e.g., close scanners)
  • Validate all inputs thoroughly

Conclusion

This project not only strengthens your understanding of Java fundamentals and data structure implementation but also showcases how abstract algorithms manifest in tangible applications like maze generation and pathfinding. By adhering to clean code standards and algorithmic correctness, students will gain both theoretical insight and practical skills in problem-solving, simulation, and user-interface visualization.

The ability to switch between depth-first and breadth-first search strategies, manipulate 2D data structures, and dynamically render graphical states under constrained libraries, makes this a robust capstone for introductory data structures in Java.

Successful completion demonstrates mastery over core Java programming constructs, data structure manipulation, and algorithmic thinking—skills essential for any software developer.