ACwing 756 Serpentine Matrix

Title description

Input two integers n and m, output a matrix with n rows and m columns, and fill the matrix with numbers 1 to n*m in a serpentine shape.

The specific matrix form can refer to the sample.

Input format

Enter a line, containing two integers n and m.

Output format

Output the matrix that meets the requirements.

The matrix occupies n rows, and each row contains m integers separated by spaces.

data range

1≤n,m≤1001≤n,m≤100

Input sample:

3 3

Sample output:

1 2 3
8 9 4
7 6 5

Assign values ​​to the places that have not been walked according to the direction of travel (bottom right and top left) 

#include <iostream>
#include <cstdio>

using namespace std;
const int MAX = 109;

int a[MAX][MAX];


int main()
{
    int n, m;

    scanf("%d%d", &n, &m);

    int sum = n * m;

    int cnt = 0;
    int row = 0;
    int col = 0;
    while(cnt < sum)
    {
        for(int i = 0; i < m; i++) // 右走
        {
            if(!a[row][i])
            {
                a[row][i] = ++ cnt;
                col = i;
            }

        }


        for(int i = row + 1; i < n; i++) // 下走
        {
            if(!a[i][col])
            {
                a[i][col] = ++cnt;
                row = i;
            }
        }

        for(int i = col - 1; i >= 0; i--) // 左走
        {
            if(!a[row][i])
            {
                a[row][i] = ++cnt;
                col = i;
            }
        }

        for(int i = row - 1; i >= 0; i--)
        {
            if(!a[i][col])
            {
                a[i][col] = ++cnt;
                row = i;
            }
        }
    }

    for(int i = 0; i < n; i++)
    {
        for(int j = 0; j < m; j++)
            printf("%d ", a[i][j]);
        printf("\n");
    }

    return 0;
}