Check out example codes for "Shortest Distance in a Maze". It will help you in understanding the concepts better.

Code Example 1

// C++ program to find the shortest path between 
// a given source cell to a destination cell. 
#include <bits/stdc++.h> 
using namespace std; 
#define ROW 9 
#define COL 10 
  
//To store matrix cell cordinates 
struct Point 
{ 
    int x; 
    int y; 
}; 
  
// A Data Structure for queue used in BFS 
struct queueNode 
{ 
    Point pt;  // The cordinates of a cell 
    int dist;  // cell's distance of from the source 
}; 
  
// check whether given cell (row, col) is a valid 
// cell or not. 
bool isValid(int row, int col) 
{ 
    // return true if row number and column number 
    // is in range 
    return (row >= 0) && (row < ROW) && 
           (col >= 0) && (col < COL); 
} 
  
// These arrays are used to get row and column 
// numbers of 4 neighbours of a given cell 
int rowNum[] = {-1, 0, 0, 1}; 
int colNum[] = {0, -1, 1, 0}; 
  
// function to find the shortest path between 
// a given source cell to a destination cell. 
int BFS(int mat[][COL], Point src, Point dest) 
{ 
    // check source and destination cell 
    // of the matrix have value 1 
    if (!mat[src.x][src.y] || !mat[dest.x][dest.y]) 
        return -1; 
  
    bool visited[ROW][COL]; 
    memset(visited, false, sizeof visited); 
      
    // Mark the source cell as visited 
    visited[src.x][src.y] = true; 
  
    // Create a queue for BFS 
    queue<queueNode> q; 
      
    // Distance of source cell is 0 
    queueNode s = {src, 0}; 
    q.push(s);  // Enqueue source cell 
  
    // Do a BFS starting from source cell 
    while (!q.empty()) 
    { 
        queueNode curr = q.front(); 
        Point pt = curr.pt; 
  
        // If we have reached the destination cell, 
        // we are done 
        if (pt.x == dest.x && pt.y == dest.y) 
            return curr.dist; 
  
        // Otherwise dequeue the front cell in the queue 
        // and enqueue its adjacent cells 
        q.pop(); 
  
        for (int i = 0; i < 4; i++) 
        { 
            int row = pt.x + rowNum[i]; 
            int col = pt.y + colNum[i]; 
              
            // if adjacent cell is valid, has path and 
            // not visited yet, enqueue it. 
            if (isValid(row, col) && mat[row][col] &&  
               !visited[row][col]) 
            { 
                // mark cell as visited and enqueue it 
                visited[row][col] = true; 
                queueNode Adjcell = { {row, col}, 
                                      curr.dist + 1 }; 
                q.push(Adjcell); 
            } 
        } 
    } 
  
    // Return -1 if destination cannot be reached 
    return -1; 
} 
  
// Driver program to test above function 
int main() 
{ 
    int mat[ROW][COL] = 
    { 
        { 1, 0, 1, 1, 1, 1, 0, 1, 1, 1 }, 
        { 1, 0, 1, 0, 1, 1, 1, 0, 1, 1 }, 
        { 1, 1, 1, 0, 1, 1, 0, 1, 0, 1 }, 
        { 0, 0, 0, 0, 1, 0, 0, 0, 0, 1 }, 
        { 1, 1, 1, 0, 1, 1, 1, 0, 1, 0 }, 
        { 1, 0, 1, 1, 1, 1, 0, 1, 0, 0 }, 
        { 1, 0, 0, 0, 0, 0, 0, 0, 0, 1 }, 
        { 1, 0, 1, 1, 1, 1, 0, 1, 1, 1 }, 
        { 1, 1, 0, 0, 0, 0, 1, 0, 0, 1 } 
    }; 
  
    Point source = {0, 0}; 
    Point dest = {3, 4}; 
  
    int dist = BFS(mat, source, dest); 
  
    if (dist != INT_MAX) 
        cout << "Shortest Path is " << dist ; 
    else
        cout << "Shortest Path doesn't exist"; 
  
    return 0; 
}

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