2048 on C++

#include <iostream>
#include <string>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <deque>
#include <unordered_map>
#include <iomanip>
#include <regex>
#include <cstdlib>
#include <cstdio>
#include <ctime>
#include <numeric>
using namespace std;
#define pii pair<long long , long long>
#define FAST ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL)
const long long dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};
const long long MAX = 1000005;
const long long MOD = 1000000009;
const int WIN_VALUE = 16;

int board[4][4];

void print_board(){
    for(int i = 0; i < 4; i++){
        for(int j = 0; j < 4; j++){
            cout << board[i][j] << "   ";
        }
        cout << "\n";
    }
}

void print_board(int x, int y){
    for(int i = 0; i < 4; i++){
        for(int j = 0; j < 4; j++){
            if(i == x and j == y){
                cout << board[i][j] << "*  ";
            }
            else cout << board[i][j] << "   ";
        }
        cout << "\n";
    }
}

void random_add(){
    vector<int> empty_cells;
    for(int i = 0; i < 16; i++){
        if(board[i / 4 ][i % 4] == 0){
            empty_cells.push_back(i);
        }
    }
    if(empty_cells.size() == 0){
        cout << "Game over! There are no more empty cells!\n";
        return;
    }
    int r1 = empty_cells[rand() % (int)empty_cells.size()];
    int r2 = rand() % 2 + 1;
    board[r1 / 4][r1 % 4] = r2 * 2;
    print_board(r1 / 4, r1 % 4);
    empty_cells.clear();
}

vector<int> move_D(){
    int ret[4][4] = {};
    for(int i = 0; i < 4; i++){
        vector<int> v;
        for(int j = 3; j >= 0; j--){
            if(board[i][j] == 0){
                continue;
            }
            v.push_back(board[i][j]);
        }
        if(v.empty()){
            continue;
        }
        else if(v.size() == 1){
            ret[i][3] = v[0];
        }
        else if(v.size() == 2){
            if(v[0] == v[1]){
                ret[i][3] = v[0] * 2;
            }
            else{
                ret[i][2] = v[1];
                ret[i][3] = v[0];
            }
        }
        else if(v.size() == 3){
            if(v[0] == v[1]){
                ret[i][2] = v[2];
                ret[i][3] = v[0] * 2;
            }
            else if(v[1] == v[2]){
                ret[i][2] = v[1] * 2;
                ret[i][3] = v[0];
            }
            else{
                for(int k = 0; k < 3; k++) ret[i][3 - k] = v[k];
            }
        }
        else{
            if(v[0] == v[1]){
                if(v[2] == v[3]){
                    ret[i][2] = v[2] * 2;
                    ret[i][3] = v[0] * 2;
                }
                else{
                    ret[i][1] = v[3];
                    ret[i][2] = v[2];
                    ret[i][3] = v[0] * 2;
                }
            }
            else if(v[1] == v[2]){
                ret[i][1] = v[3];
                ret[i][2] = v[1] * 2;
                ret[i][3] = v[0];
            }
            else if(v[2] == v[3]){
                ret[i][1] = v[2] * 2;
                ret[i][2] = v[1];
                ret[i][3] = v[0];
            }
            else{
                for(int k = 0; k < 4; k++) ret[i][3 - k] = v[k];
            }
        }
    }
    vector<int> tmp;
    for(int i = 0; i < 4; i++){
        for(int j = 0; j < 4; j++){
            tmp.push_back(ret[i][j]);
        }
    }
    return tmp;
}

vector<int> move_A(){
    int ret[4][4] = {};
    for(int i = 0; i < 4; i++){
        vector<int> v;
        for(int j = 0; j < 4; j++){
            if(board[i][j] == 0){
                continue;
            }
            v.push_back(board[i][j]);
        }
        if(v.empty()){
            continue;
        }
        else if(v.size() == 1){
            ret[i][0] = v[0];
        }
        else if(v.size() == 2){
            if(v[0] == v[1]){
                ret[i][0] = v[0] * 2;
            }
            else{
                ret[i][1] = v[1];
                ret[i][0] = v[0];
            }
        }
        else if(v.size() == 3){
            if(v[0] == v[1]){
                ret[i][1] = v[2];
                ret[i][0] = v[0] * 2;
            }
            else if(v[1] == v[2]){
                ret[i][1] = v[1] * 2;
                ret[i][0] = v[0];
            }
            else{
                for(int k = 0; k < 3; k++) ret[i][k] = v[k];
            }
        }
        else{
            if(v[0] == v[1]){
                if(v[2] == v[3]){
                    ret[i][1] = v[2] * 2;
                    ret[i][0] = v[0] * 2;
                }
                else{
                    ret[i][2] = v[3];
                    ret[i][1] = v[2];
                    ret[i][0] = v[0] * 2;
                }
            }
            else if(v[1] == v[2]){
                ret[i][2] = v[3];
                ret[i][1] = v[1] * 2;
                ret[i][0] = v[0];
            }
            else if(v[2] == v[3]){
                ret[i][2] = v[2] * 2;
                ret[i][1] = v[1];
                ret[i][0] = v[0];
            }
            else{
                for(int k = 0; k < 4; k++) ret[i][k] = v[k];
            }
        }
    }
    vector<int> tmp;
    for(int i = 0; i < 4; i++){
        for(int j = 0; j < 4; j++){
            tmp.push_back(ret[i][j]);
        }
    }
    return tmp;
}
vector<int> move_W(){
    int ret[4][4] = {};
    for(int j = 0; j < 4; j++){
        vector<int> v;
        for(int i = 0; i < 4; i++){
            if(board[i][j] == 0){
                continue;
            }
            v.push_back(board[i][j]);
        }
        if(v.empty()){
            continue;
        }
        else if(v.size() == 1){
            ret[0][j] = v[0];
        }
        else if(v.size() == 2){
            if(v[0] == v[1]){
                ret[0][j] = v[0] * 2;
            }
            else{
                ret[1][j] = v[1];
                ret[0][j] = v[0];
            }
        }
        else if(v.size() == 3){
            if(v[0] == v[1]){
                ret[1][j] = v[2];
                ret[0][j] = v[0] * 2;
            }
            else if(v[1] == v[2]){
                ret[1][j] = v[1] * 2;
                ret[0][j] = v[0];
            }
            else{
                for(int k = 0; k < 3; k++) ret[k][j] = v[k];
            }
        }
        else{
            if(v[0] == v[1]){
                if(v[2] == v[3]){
                    ret[1][j] = v[2] * 2;
                    ret[0][j] = v[0] * 2;
                }
                else{
                    ret[2][j] = v[3];
                    ret[1][j] = v[2];
                    ret[0][j] = v[0] * 2;
                }
            }
            else if(v[1] == v[2]){
                ret[2][j] = v[3];
                ret[1][j] = v[1] * 2;
                ret[0][j] = v[0];
            }
            else if(v[2] == v[3]){
                ret[2][j] = v[2] * 2;
                ret[1][j] = v[1];
                ret[0][j] = v[0];
            }
            else{
                for(int k = 0; k < 4; k++) ret[k][j] = v[k];
            }
        }
    }
    vector<int> tmp;
    for(int i = 0; i < 4; i++){
        for(int j = 0; j < 4; j++){
            tmp.push_back(ret[i][j]);
        }
    }
    return tmp;
}

vector<int> move_S(){
    int ret[4][4] = {};
    for(int j = 0; j < 4; j++){
        vector<int> v;
        for(int i = 3; i >= 0; i--){
            if(board[i][j] == 0){
                continue;
            }
            v.push_back(board[i][j]);
        }
        if(v.empty()){
            continue;
        }
        else if(v.size() == 1){
            ret[3][j] = v[0];
        }
        else if(v.size() == 2){
            if(v[0] == v[1]){
                ret[3][j] = v[0] * 2;
            }
            else{
                ret[2][j] = v[1];
                ret[3][j] = v[0];
            }
        }
        else if(v.size() == 3){
            if(v[0] == v[1]){
                ret[2][j] = v[2];
                ret[3][j] = v[0] * 2;
            }
            else if(v[1] == v[2]){
                ret[2][j] = v[1] * 2;
                ret[3][j] = v[0];
            }
            else{
                for(int k = 0; k < 3; k++) ret[3 - k][j] = v[k];
            }
        }
        else{
            if(v[0] == v[1]){
                if(v[2] == v[3]){
                    ret[2][j] = v[2] * 2;
                    ret[3][j] = v[0] * 2;
                }
                else{
                    ret[1][j] = v[3];
                    ret[2][j] = v[2];
                    ret[3][j] = v[0] * 2;
                }
            }
            else if(v[1] == v[2]){
                ret[1][j] = v[3];
                ret[2][j] = v[1] * 2;
                ret[3][j] = v[0];
            }
            else if(v[2] == v[3]){
                ret[1][j] = v[2] * 2;
                ret[2][j] = v[1];
                ret[3][j] = v[0];
            }
            else{
                for(int k = 0; k < 4; k++) ret[3 - k][j] = v[k];
            }
        }
    }
    vector<int> tmp;
    for(int i = 0; i < 4; i++){
        for(int j = 0; j < 4; j++){
            tmp.push_back(ret[i][j]);
        }
    }
    return tmp;
}

bool check(vector<int> vec){
    for(auto x : vec){
        if(x == 0){
            return true;
        }
    }
    return false;
}

bool check2(){
    for(int i = 0; i < 4; i++){
        for(int j = 0; j < 4; j++){
            if(board[i][j] == 0){
                return true;
            }
        }
    }
    return false;
}

bool check3(vector<int> vec){
    vector<int> tmp;
    for(int i = 0; i < 4; i++){
        for(int j = 0; j < 4; j++){
            tmp.push_back(board[i][j]);
        }
    }
    for(int i = 0; i < 16; i++){
        if(vec[i] != tmp[i]){
            return true;
        }
    }
    return false;
}

void apply(vector<int> vec){
    for(int i = 0; i < 16; i++){
        board[i / 4][i % 4] = vec[i];
    }
}

int main() {
    //freopen("hayfeast.in", "r", stdin);
    //freopen("hayfeast.out", "w", stdout);
    FAST;
    cout << "Welcome to 2048!\nType W, A, S, or D to move the tiles.\nTiles with the same number merge into one when they touch.\nAdd them up to reach 2048!\nNewly added numbers have a \"*\" behind it.\nType \"EXIT\" to exit the game\n";
    random_add();
    while(true){
        string c;
        cin >> c;
        if(c == "EXIT"){
            cout << "You have successfully exited 2048!\n";
            break;
        }
        map<string, bool> m;
        bool ck = check2();
        bool pos = false;
        map<string, vector<int>> m2;
        m2["D"] = move_D();
        m2["A"] = move_A();
        m2["W"] = move_W();
        m2["S"] = move_S();
        if(!ck){
            m["D"] = check(m2["D"]);
            m["A"] = check(m2["A"]);
            m["W"] = check(m2["W"]);
            m["S"] = check(m2["S"]);
            pos = m["D"] || m["A"] || m["W"] || m["S"];
        }
        if(c != "D" and c!= "A" and c != "W" and c != "S"){
            cout << "You have to type in W, A, S, or D in their capital forms!\n";
        }
        else{
            if(!ck and pos and !m[c]){
                cout << "You will lose if you swipe this way!\nChoose a different direction to swipe!\n";
            }
            else if(!check3(m2[c])){
                cout << "This move doesn't do anything!\nChoose a different direction to swipe!\n";
            }
            else{
                apply(m2[c]);
                random_add();
            }
        }
        for(int i = 0; i < 4; i++){
            for(int j = 0; j < 4; j++){
                if(board[i][j] == WIN_VALUE){
                    cout << "Congratulations!\nYou won!!!\n";
                    return 0;
                }
            }
        }
    }
}