Language: C++

#include <bits/stdc++.h>

#define REP(i, n) for(int i = 0;i < n;i++)
#define REPR(i, n) for(int i = n;i >= 0;i--)
#define FOR(i, m, n) for(int i = m;i < n;i++)
#define FORR(i, m, n) for(int i = m;i >= n;i--)
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define INF 999999999
#define M_PI 3.14159265358979323846
#define ALL(X) (X).begin(),(X).end()

#ifdef __LOCAL
    #define DBG(X) cout << #X << " = " << (X) << endl;
    #define SAY(X) cout << (X) << endl;
#else
    #define DBG(X)
    #define SAY(X)
#endif

#ifdef __LOCAL
    #include <filesystem>
    namespace fs = std::filesystem;
#endif

using namespace std;

using ll = long long int;
using ull = unsigned long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

int dx[]={1, 0, -1, 0, 0};
int dy[]={0, 1, 0, -1, 0};
const int INT_INF = (int)(2e9);
const ll  LL_INF = (ll)(2e18);
const int NIL = -1;
static mt19937 _g(time(nullptr));
 
std::string pad(int num){ char buffer[4]; std::snprintf(buffer, sizeof(buffer), "%03d", num); return buffer;}
inline ll randint(ll a, ll b) { ll w = (_g() << 31LL) ^ _g(); return a + w % (b - a + 1); }
inline void fast_io() { ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); };
template<typename T> inline T sign(T x) { return T(x > 0) - T(x < 0); }
template<typename T, typename S> inline ostream& operator<<(ostream& os, const pair<T, S> p) { cout << "[" << p.first << ";" << p.second << "]"; return os; }
template<typename T> inline ostream& operator<<(ostream& os, const vector<T>& v) { for (auto el : v) cout << el << " "; return os; }
template<typename T> inline T fetch() { T ret; cin >> ret; return ret; }
template<typename T> inline vector<T> fetch_vec(int sz) { vector<T> ret(sz); for (auto& elem : ret) cin >> elem; return ret; }

int H,W,A,B;

void input(){
    fast_io();
    #ifdef __LOCAL
        fs::path p = __FILE__;
        fs::path input,output;
        input = output = p.parent_path();
        input += string("/input/") + string(p.stem()) + string(".txt");
        output += string("/output/") + string(p.stem()) + string(".txt");
        freopen(input.c_str(), "r", stdin);
        freopen(output.c_str(), "w", stdout);
    #endif
    cin >> H >> W >> A >> B;
}

void showAns(vector<vector<int>> ans){
    for(auto aH:ans) {{for(auto a:aH) cout << a;} cout << endl;}
}

bool isOk(vector<vector<int>> ans){
    for (int i = 0; i < H; i++)
    {
        int row=0;
        row = accumulate(ALL(ans[i]),0);
        if(row==A || row==(W-A)) continue;
        else return false;
    }
    for (int j = 0; j < W; j++)
    {
        int column=0;
        for (int i = 0; i < H; i++)
        {
            column += ans[i][j];
        }
        if(column==B || column==(H-B)) continue;
        else return false;
    }
    return true;    
}

int solve(){
    vector<vector<int>> ans(H,vector<int>(W,0));
    vector<vector<int>> zero = ans;
    if(A==0&&B==0) {showAns(zero); return 0;}
    if(A==0&&B>0) {
        // 1111
        // 1111
        // 0000
        for (int i = 0; i < B; i++)
        {
            for (int j = 0; j < W; j++)
            {
                ans[i][j]=1;
            }
            
        }
        showAns(ans);        
        return 0;
        }
    if(A>0&&B==0) {
        // 11000
        // 11000
        // 11000
        for (int i = 0; i < H; i++)
        {
            for (int j = 0; j < A; j++)
            {
                ans[i][j]=1;
            }
            
        }
        showAns(ans);
        return 0;
        }

    int last=0;
    // 11000
    // 11000
    // 00110
    // 00110
    // 10001
    for (int i = 0; i < H; i++)
    {
        for (int j = 0; j < A; j++)
        {
            ans[i][(j+last)%W]=1;
        }
        if((i+1)%B==0) last+=A;
    }
    if(isOk(ans)) {showAns(ans); return 0;}
    // else cout << "No" << endl;
    ans = zero;
    int cnt=0;
    // 11000
    // 11000
    // 11000
    // 00110
    for (int i = 0; i < H; i++)
    {
        for (int j = 0; j < A; j++)
        {
            ans[i][(j+last)%W]=1;
        }
        if(i<H-B-1) continue;
        if(i==H-B-1) last += A;
        if(i>=H-B) {cnt++;if(cnt&B==0) last+=A;}
    }
    if(isOk(ans)) {showAns(ans); return 0;}
    // 111100
    // 111100
    // 000011
    // 000011
    ans = zero;
    int cnt=0;
    for (int j = 0; j < W; j++)
    {
        for (int i = 0; i < B; i++)
        {
            ans[(i+last)%H][j]=1;
        }
        if(j<W-A-1) continue;
        if(j==W-A-1) last += B;
        if(j>=W-A) {cnt++; if(cnt&A==0) last+=B;}
    }

    if(isOk(ans)) {showAns(ans); return 0;}
    else cout << "No" << endl;
    return 0;
}

int main()
{
    input();
    solve();
    return 0;
}


Compiler output:
a.cc: In function 'int solve()':
a.cc:164:9: error: redeclaration of 'int cnt'
  164 |     int cnt=0;
      |         ^~~
a.cc:143:9: note: 'int cnt' previously declared here
  143 |     int cnt=0;
      |         ^~~