Distance_of_nearest_cell_having_1.cpp

//{ Driver Code Starts
#include <bits/stdc++.h>
using namespace std;


// } Driver Code Ends
class Solution {
  public:
    // Function to find distance of nearest 1 in the grid for each cell.
    vector<vector<int>> nearest(vector<vector<int>>& grid) {
        int n = grid.size();
        int m = grid[0].size();
        
        int rdir[] = {-1, 0, +1, 0};
        int cdir[] = {0, +1, 0, -1};
        
        vector<vector<int>> vis(n, vector<int>(m, 0));
        vector<vector<int>> dist(n, vector<int>(m, 0));
        queue<pair<pair<int, int>, int>> q;
        
        for(int row = 0; row < n; row++)
        {
            for(int col = 0; col < m; col++)
            {
                if(grid[row][col] == 1)
                {
                    vis[row][col] = 1;
                    q.push({{row, col}, 0});
                }
            }
        }
        
        while(!q.empty())
        {
            int row = q.front().first.first;
            int col = q.front().first.second;
            int steps = q.front().second;
            dist[row][col] = steps;
            q.pop();
            for(int i = 0; i < 4; i++)
            {
                int nrow = row + rdir[i];
                int ncol = col + cdir[i];
                
                if(nrow >= 0 && nrow < n && ncol >= 0 && ncol < m 
                    && vis[nrow][ncol] == 0)
                {
                    vis[nrow][ncol] = 1;
                    q.push({{nrow, ncol}, steps+1});
                }
            }
        }
        return dist;
    }
};

//{ Driver Code Starts.
int main() {
    int tc;
    cin >> tc;
    while (tc--) {
        int n, m;
        cin >> n >> m;
        vector<vector<int>> grid(n, vector<int>(m, -1));
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; j++) {
                cin >> grid[i][j];
            }
        }
        Solution obj;
        vector<vector<int>> ans = obj.nearest(grid);
        for (auto i : ans) {
            for (auto j : i) {
                cout << j << " ";
            }
            cout << "\n";
        }
    }
    return 0;
}
// } Driver Code Ends