1207B - Square Filling - CodeForces Solution

constructive algorithms greedy implementation *1200

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Python Code: 

from sys import stdin
input = stdin.readline

inp = lambda : list(map(int,input().split()))

def check(x , y):

    if(x + 1 >= n or y + 1 >= m):return False

    count = a[x][y] + a[x + 1][y] + a[x][y + 1] + a[x + 1][y + 1]
    if(count == 4):return True

    return False

def answer():

    ans = []
    b = [[0 for i in range(m)] for j in range(n)]
    for i in range(n):
        for j in range(m):

            if(check(i , j)):
                b[i][j] = 1
                b[i + 1][j] = 1
                b[i][j + 1] = 1
                b[i + 1][j + 1] = 1
                ans.append([i + 1 , j + 1])

            if(b[i][j] == 0 and a[i][j] == 1):
                if(not check(i , j)):
                    print(-1)
                    return 

    print(len(ans))
    for x in ans:
        print(*x)
    

for T in range(1):

    n , m = inp()
    a = [inp() for i in range(n)]

    answer()

C++ Code: 

#include <bits/stdc++.h>
using namespace std;
vector<pair<int , int>> operations;
void check(vector<vector<int>> &v , int x , int y)
{
    int total = v[x][y] + v[x + 1][y] + v[x][y + 1] + v[x + 1][y + 1];
    if(total == 4) operations.push_back({x , y});
}


void testcase()
{
    int n , m; cin >> n >> m;
    vector<vector<int>> v(n , vector<int>(m , 0));
    for(auto &vec : v) for(auto &i : vec) cin >> i;

    for (int i = 0; i < n - 1; ++i)
    {
        for (int j = 0; j < m - 1 ; ++j)
        {
            check(v , i , j);
        }
    }
    

    vector<vector<int>> dup(n , vector<int>(m , 0));

    for(auto &[x , y] : operations)
    {
        int a = x , b = y;

        dup[x][y] = 1;
        dup[x + 1][y] = 1;
        dup[x][y + 1] = 1;
        dup[x + 1][y + 1] = 1;
    }

    if(dup == v)
    {
        cout << operations.size() << endl;
        for(auto &[x , y] : operations)
        {
            cout << x + 1 << " " << y + 1 << endl;
        }
    }
    else cout << -1 << endl;
}

int main() 
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    
    clock_t z = clock();

    int tc = 1;
    // cin >> tc;
    while (tc--) testcase();

    cerr << "Run Time : " << ((double)(clock() - z) / CLOCKS_PER_SEC) << endl;
    return 0;
}


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