UNO.ai: Islands - m x n 2D binary grid

Unoai_main_1.cpp

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

// Initialize helper data structures and visited array.
vector<int> x{-1, 1, 0, 0};
vector<int> y{0, 0, -1, 1};
int visited[1000][1000] = {0};

// If its a visited node, then ignore. 
// If the element is 0 then ignore as there is no island on that path, i.e. the coast.
int isvalid(int i, int j, vector<vector<char>>& grid){
    if(i<0 || j<0 || i>=grid.size() || j>=grid[0].size()) return 0;
    if(visited[i][j] == 1)  return 0;
    if(grid[i][j] == '0') return 0;
    
    // return 1 if its a valud land piece
    return 1; 
}

int dfs(int i, int j, vector<vector<char>>& grid){
    // Ignore if visited, if not then visit it.
    if(visited[i][j] == 1)  return 0;
    visited[i][j] = 1;
    
    // Check in all 4 directions of the current land piece.
    for(int k=0; k<4; k++){
        int valid = isvalid(i+x[k],j + y[k], grid);
        if (valid == 0) continue;
        int a = dfs(i+x[k], j+ y[k], grid);
    }
    
    return 0;
}

int numIslands(vector<vector<char>>& grid) {
    int m = grid.size();
    int n = grid[0].size();
    
    // Iterate all land pieces and call function for all those that are not visited and actually land.
    int ans = 0;
    for(int i=0; i<m; i++){
        for(int j=0; j<n; j++){
            if(grid[i][j] == '1' && visited[i][j] == 0) {
                int is_island = dfs(i, j, grid);
                ans += 1;
            }
        }
    }
    return ans;
}

// Take inputs from the user, process and display output.
int main(){
    
    vector<vector<char>> islands;
    
    cout<<"\nEnter size of islands in m, n:\n";
    int m, n;
    cin>>m>>n;
    
    cout<<"\nEnter the terrain info in 1, 0 fashion in an mxn grid: \n";
    for(int i=0; i<m; i++){
        vector<char> temp;
        for(int j=0; j<n; j++){
            int x; cin>>x;
            if(x==0)    temp.push_back('0');
            else temp.push_back('1');
        }
        islands.push_back(temp);
    }
    
    int ans = numIslands(islands);
    cout<<"\nNumber of islands = "<<ans;
    return 0;
}