拒绝使用常规方法

#include<bits/stdc++.h>
using namespace std;

int main()
{
    int n,m;
    cin >> n >> m;
    int a[n][m];
    bool b[n][m];
    for (int i=0;i<n;i++)
    {
        for (int j=0;j<m;j++)
        {
            b[i][j]=0;
            cin >> a[i][j];
        }
    }
    b[0][0]=1;
    for (int i=0;i<n;i++)
    {
        for (int j=0;j<m;j++)
        {
            if (a[i][j]==0)
            {
                if (i>0) b[i][j]=b[i][j] || b[i-1][j];
                if (i<n-1) b[i][j]=b[i][j] || b[i+1][j];
                if (j>0) b[i][j]=b[i][j] || b[i][j-1];
                if (j<m-1) b[i][j]=b[i][j] || b[i][j+1];
            }
        }
    }
    if (b[n-1][m-1])
        cout << "YES";
    else
        cout << "NO";
    return 0;
}