简单算法

int main(int argc, char *argv[])
{
        int i=1;
        int delta=1;
        while(1){
              printf( "%d\n", i );
              i += delta;
              if ( delta == 1 && i == 10 ){
                  delta = -1;
              }
              else if ( delta == -1 && i == 1 ){
                  delta = 1;
              }

        }
        return 0;
}