지그재그 배열 채우기

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#include <iostream>
#include <cstring>
using namespace std;


int main() 
{
    int a;
    int arr[4][4]; 
    cin >> a;
    for (int y = 0; y < 4; y++) {
        if (y % 2 == 0) {
            for (int x = 0; x < 4; x++) {
                arr[y][x] = a++;
            }
        }
        else if (y % 1 == 0) {
            for (int x = 3; x >= 0; x--) {
                arr[y][x] = a++; 
            }
        }
    }

    for (int y = 0; y < 4; y++) {
        for (int x = 0; x < 4; x++) {
            cout << arr[y][x] << " ";
        } cout << endl; 
    }


     return 0;
}