Proposed by: under_score_07 ~~~~~ int x=0,y=1,i=0,j=0; while(1) { cout<<i<<" "<<j<<endl; if(x==0 and y==1) { if(j==m-1) x=1,y=0; } else if(x==1 and y==0) { if(i==n-1) x=0,y=-1; } else if(x==0 and y==-1) { if(j==0) x=-1,y=0; } i+=x,j+=y; if(i==0 and j==0) break; } } ~~~~~

Proposed by: bthero ~~~~~ bool inside(int x, int y) { return 0 <= x && x < n && 0 <= y && y < m; }

int dx[] = {0, 1, 0, -1}; int dy[] = {1, 0, -1, 0};

int x = 0, y = 0, d = 0;

do { // do stuff with (x, y)

if (!inside(x + dx[d], y + dy[d])) {
    d++;
}

x += dx[d];
y += dy[d];

} while (x != 0 || y != 0); ~~~~~

for(int x = 0; x < n * m; x++) {
    int i = x / m, j = x % m;
    cout << i << ' ' << j << '\n';
    x += (m - 2) * (m != 1 && i != 0 && i != n - 1 && j == 0);
}