[In a hurry] I don't know why there's an infinite loop in finding n-queen using c language

i--;

while (i = !0)
{
    if (board[i][j] == 1) return 0;
    i--;
}

i = (num-1);

while (i = !0 && j+k <= size)
{
    if (board[i][j + k] == 1) return 0;
    k++;
    i--;
}

i = (num-1);
k = 1;

while (i = !0 && j-k >0)
{
    if (board[i][j - k] == 1) return 0;
    k++;
    i--;
}

return 1;