Comp 1672, Winter 2003
Homework Assignment 1
Solutions

1a) The colon on the 3rd line should be a semi-colon.
    The (x=1) on the 4th line should be (x==1).
    The "otherwise" on the 6th line should be "else"
1b) The "For" should be "for"
    The commas should be semicolons
    The x++ should be x-- instead (otherwise you get an infinite loop
lc) The case 0 segment is missing a break.  (Even better, put a break
    statement at the end of each case.)
1d) The logic in the while statement is wrong.  It should say
    while (answer < 0 || answer > 1)

2.  For each value of i, 5-i+1 X's are output.  This gives
    6+5+4+3+2=20 X's

3.  The trick here is that there is a semi-colon after the for statement.
    This means that the for-loop has an empty body - NOTHING happens each
    repetition of the for-loop, except that ctr is incremented.  At the
    final increment, ctr==20, and at that point the for-loop terminates.
    Then ctr is output.  The value output is 20.

4. int power(int base, int exponent)
   {
       int i;
       int result=1;
       for (i=1; i <= exponent ; i++)
           result *= base;
       return result;
   }

5. // return the value of the nth fibonacci number.  The value of n should
   // be 1 or greater.  Return 0 for invalid inputs.
   int fibonacci(int n)
   {
       int i, prev(1), prevprev(1), current;

       if (n <=0) return 0;           // invalid input - return 0
       if (n == 1 || n == 2)          // The first two values of the sequence
           return 1;                  // are both equal to 1
       for (i=3; i <= n; i++) {       // If n >= 3, then calculate all values
                                      // starting at 3 until we get to n
           current = prev+prevprev;   // Add previous two values to get the next
           prevprev=prev;             // Then update the two previous ones
           prev=current;
       }
       return current;
   }