NAQ22 E Solution (C++)

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

using namespace std;

int n,m;
vector<string> arr;
vector<vector<bool>> vis;

// indices in bounds
bool val(int x,int y)
{
    return 0<=x && x<n && 0<=y && y<m;
}

int dfs(char c, int x,int y)
{
    vis[x][y] = true;

    int sum = 0;
    if(arr[x][y]=='.') sum++;

    vector<pair<int,int>> dirs = {{-1,0},{1,0},{0,-1},{0,1}};

    for(auto dir:dirs)
    {
        int xc = x+dir.first;
        int yc = y+dir.second;

        if(val(xc,yc) && (arr[xc][yc]==c || arr[xc][yc]==' ' || arr[xc][yc]=='.' ) && !vis[xc][yc])
        {
            sum += dfs(c, xc,yc);
        }

    }
    return sum;
}

int main()
{
    cin>>n>>m;
    arr.resize(n);
    vis.assign(n, vector<bool>(m));

    getline(cin, arr[0]);

    for(int i=0;i<n;i++) getline(cin,arr[i]);

    // total number of dots
    int total = 0;
    for(int i=0;i<n;i++) for(int j=0;j<m;j++) if(arr[i][j]=='.') total++;

    // number of dots found
    int cur = 0;
    int need = 0;

    for(int i=0;i<n;i++)
    {
        for(int j=0;j<m;j++)
        {
            // it its a letter A-W
            if( 0<=(arr[i][j]-'A') && (arr[i][j]-'A') <= 22 )
            {
                int found = dfs(arr[i][j],i,j);
                // if we find at least 1 new dot
                if(found>0)
                {
                    need++;
                    total -= found;
                }
            }
        }
    }

    cout << need << ' '<<total<<'\n';

}