Мусор в двумерном массиве

#include <iostream>
#include <ctime>
#include <cstdlib>
using namespace std;
int LStep, CStep, LStart, CStart;
int board[4][4];
pair <int, int> generateUnoccupiedPosition() {
    int occupied = 1, line, column;
    while (occupied) {
        line = rand() % 4;
        column = rand() % 4;
        if (board[line][column] == 0)
            occupied = 0;
    }
    return make_pair(line, column);
}
void newGame() {
    for (int i = 0; i < 4; ++i)
        for (int j = 0; j < 4; ++j)
            board[i][j] = 0;
    pair <int, int> pos = generateUnoccupiedPosition();
    board[pos.first][pos.second] = 2;
}
void printUI() {
    for (int i = 0; i < 4; ++i) {
        for (int j = 0; j < 4; ++j)
            if (board[i][j] == 0)
                cout << ".";
            else
                cout << board[i][j];
        cout << "\n";
    }
    cout << "n: new game, w: up,s: down, d: right, a: left,q:quit \n";
}
 
void moveW() {
 
    for (int j = 0; j < 4; ++j)
        for (int i = 3; i > 0; --i) {
            if (board[i - 1][j] = 0 || (board[i - 1][j] == board[i][j])) {
                board[i - 1][j] += board[i][j];
                board[i][j] = 0;
            }
        }
 
}
int main() {
    srand(time(0));
    newGame();
    while (true) {
        printUI();
        char command;
        cin >> command;
        if (command == 'n')
            newGame();
        else if (command == 'q')
            break;
        if (command == 'w') moveW();
    }
    return 0;

if (board[i - 1][j] = 0 || (board[i - 1][j] == board[i][j]))

        cin >> command;
        cin.get();