if (statement[i]=='0' || statement[i]=='1')
{
    if (statement[i+1]!='&' || statement[i+1]!='|' || statement[i+1]!=')')
        return 0;
}
if (statement[i]=='&' || statement[i]=='|')
{
    if (statement[i+1]!='1' || statement[i+1]!='0' || statement[i+1]!='(')
        return 0;
}
if (statement[i]=='(' && statement[i+4]==')')
{
  .......
and the following loop:
    for (t=i; t<length; t++)
    {
        if (statement[t]==')')
        {
            return check_statement (statement, length, t-i+1);
        }
    }
}
return 1;