c++ code not giving output (topic : recursion and 2D vector)

Question

1. You are given a number n, representing the number of rows.
2. You are given a number m, representing the number of columns.
3. You are given n*m numbers, representing elements of 2d array a. The numbers can be 1 or 0 only.
4. You are standing in the top-left corner and have to reach the bottom-right corner. Only four moves are allowed 't' (1-step up), 'l' (1-step left), 'd' (1-step down) 'r' (1-step right). You can only move to cells which have 0 value in them. You can't move out of the boundaries or in the cells which have value 1 in them (1 means obstacle)
5. Complete the body of floodfill function - without changing signature - to print all paths that can be used to move from top-left to bottom-right.

this is the question and here is the link for reference https://www.pepcoding.com/resources/online-java-foundation/recursion-backtracking/flood-fill-official/ojquestion#

i used the following code and checked it many times i dont find any error in it please help me figure out whats wrong, i am coding in c++

#include <iostream>
#include <string>
#include <vector>

using namespace std;

void floodfill(vector<vector<int>> maze, int sr, int sc, string psf, vector<vector<int>> visited)
{
    if (sr < 0 || sc < 0 || sr == maze.size() || sc == maze[0].size() ||
        maze[sr][sc] == 1 || visited[sr][sc] == 1)
            return;
    if (sr == maze.size() - 1 && sc == maze[0].size() - 1)
    {
        cout << psf << endl;
        return;
    }
    visited[sr][sc] == 1;
    floodfill(maze, sr - 1, sc, psf + "t", visited);
    floodfill(maze, sr, sc - 1, psf + "l", visited);
    floodfill(maze, sr + 1, sc, psf + "d", visited);
    floodfill(maze, sr, sc + 1, psf + "r", visited);
    visited[sr][sc] == 0;
}

int main()
{
    int n, m;
    cin >> n >> m;
    vector<vector<int>> arr(n, vector<int>(m));
    vector<vector<int>> visited(n, vector<int>(m));
    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++)
            cin >> arr[i][j];

    floodfill(arr, 0, 0, "", visited);
}

please someone help thnx..

Answer 1

You need to add references to your vectors. C and C++ are pass by value languages you need to explicitly tell C++ that you are passing by reference.

void floodfill(vector<vector<int>>& maze, int sr, int sc, string psf, vector<vector<int>>& visited)
{
    if (sr < 0 || sc < 0 || sr == maze.size() || sc == maze[0].size() ||
        maze[sr][sc] == 1 || visited[sr][sc] == 1)
            return;
    if (sr == maze.size() - 1 && sc == maze[0].size() - 1)
    {
        cout << psf << endl;
        return;
    }
    visited[sr][sc] = 1;
    floodfill(maze, sr - 1, sc, psf + "t", visited);
    floodfill(maze, sr, sc - 1, psf + "l", visited);
    floodfill(maze, sr + 1, sc, psf + "d", visited);
    floodfill(maze, sr, sc + 1, psf + "r", visited);
    visited[sr][sc] = 0;
}

Also I think you may want to do assignment here visited[sr][sc] == 1;