Algorithms/Maze.cpp at main · MohammadFahad1/Algorithms · GitHub

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#include <bits/stdc++.h>
using namespace std;

const int N = 1e3 + 10;
bool vis[N][N];
int dx[4] = {0, 0, -1, 1};
int dy[4] = {1, -1, 0, 0};
map<pair<int, int>, pair<int, int>> par;

int n, m;
char graph[N][N];

bool valid(int ci, int cj)
{
    if (ci >= 0 && ci < n && cj >= 0 && cj < m && graph[ci][cj] != '#')
    {
        return true;
    }
    else
    {
        return false;
    }
}

void bfs(int si, int sj)
{
    vis[si][sj] = true;
    queue<pair<int, int>> q;
    q.push({si, sj});

    while (!q.empty())
    {
        pair<int, int> node = q.front();
        q.pop();

        for (int i = 0; i < 4; i++)
        {
            int ci = node.first + dx[i];
            int cj = node.second + dy[i];

            if (valid(ci, cj) && !vis[ci][cj])
            {
                vis[ci][cj] = true;
                q.push({ci, cj});
                par[{ci, cj}] = {node.first, node.second};
                if (graph[ci][cj] == 'D')
                {
                    return;
                }
            }
        }
    }
}

int main()
{
    cin >> n >> m;

    memset(vis, false, sizeof(vis));

    pair<int, int> start, end;

    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < m; j++)
        {
            cin >> graph[i][j];
            if (graph[i][j] == 'R')
            {
                start = {i, j};
            }
            if (graph[i][j] == 'D')
            {
                end = {i, j};
            }
        }
    }

    bfs(start.first, start.second);

    if (vis[end.first][end.second])
    {
        int xi = end.first;
        int xj = end.second;

        while (graph[xi][xj] != 'R')
        {
            pair<int, int> p = par[{xi, xj}];
            xi = p.first;
            xj = p.second;

            if (graph[xi][xj] != 'R')
            {
                graph[xi][xj] = 'X';
            }
        }
    }

    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < m; j++)
        {
            cout << graph[i][j];
        }
        cout << endl;
    }

    return 0;
}