756. Serpentine matrix

subject

Enter two integers n and m, Output one n That's ok m Columns of the matrix , The digital 1 To n×m Fill the matrix in the shape of a serpentine .

For the specific matrix form, please refer to the example .

Input format
Enter a total of one line , Contains two integers n and m.

Output format
Output a matrix that meets the requirements .

Matrix occupation n That's ok , Each row contains m An integer separated by spaces .

Data range
1≤n,m≤100
sample input ：
3 3
sample output ：
1 2 3
8 9 4
7 6 5

Code

#include <iostream>

using namespace std;

int q[110][110];

int main()
{
    
    int n, m;
    cin >> n >> m;
    
    
    int dx[] = {
    -1,0,1,0}, dy[] = {
    0,1,0,-1};
    int d = 1;
    
    int x = 0, y = 0;
    for(int i = 1; i <= n*m; i++)
    {
    
        q[x][y] = i;
        int ne_x = x + dx[d], ne_y = y + dy[d];
        if(ne_x < 0 || ne_x >= n || ne_y < 0 || ne_y >= m || q[ne_x][ne_y])
        {
    
            d = (d+1) % 4;
            ne_x = x+dx[d], ne_y = y+dy[d];
        }
        x = ne_x, y = ne_y;
    }
    
    for(int i = 0; i < n; i++)
    {
    
        for(int j = 0; j < m; j++)
            printf("%d ",q[i][j]);
        printf("\n");
    }
    
    
    return 0;
}