Transcript presentation source

Lecture 26
Final review
Problem 1 (10 points)
How many times would the FOR-DO loops beginning with
the following statements be executed? If the loop is
invalid, write invalid and give the reason.
_____ a. FOR J:= 0 TO 0 DO
_____ b. FOR J:= 1 DOWNTO 5 DO
_____ c. FOR CH:= '#' TO 7 DO
_____ d. FOR J:= '1' TO '5' DO
_____ e. FOR CH:= 5 DOWNTO 3 DO
Problem 1 (10 points)
How many times would the FOR-DO loops beginning with
the following statements be executed? If the loop is
invalid, write invalid and give the reason.
__1___
a. FOR J:= 0 TO 0 DO
__0___
b. FOR J:= 1 DOWNTO 5 DO
_invalid_
c. FOR CH:= '#' TO 7 DO (types mismatch)
__5___
d. FOR J:= '1' TO '5' DO
__3___
e. FOR CH:= 5 DOWNTO 3 DO
Problem 2 (10 points)
How many times would the write beginning in the
following statements be executed? If the loop is invalid,
write invalid. and give the reason.
A)
FOR J:= 3 DOWNTO 1 DO BEGIN
FOR K:= 1 TO 3 DO BEGIN
write('*')
END;
writeln
END
Problem 2 (10 points)
How many times would the write beginning in the
following statements be executed? If the loop is invalid,
write invalid. and give the reason.
A)
FOR J:= 3 DOWNTO 1 DO BEGIN
The outer loop will be
FOR K:= 1 TO 3 DO BEGIN
executed 3 times.
write('*')
The inner loop will be
END;
executed 3 times as well.
Writeln
Therefore, write will be
END
called 9 times (3*3) and
writeln 3 times.
Problem 2 (10 points)
How many times would the write beginning in the
following statements be executed? If the loop is invalid,
write invalid. and give the reason.
B)
FOR J:= 1 TO 3 DO BEGIN
FOR K:= J TO 1 DO BEGIN
write('*')
END;
writeln
END
Problem 2 (10 points)
How many times would the write beginning in the
following statements be executed? If the loop is invalid,
write invalid. and give the reason.
B)
FOR J:= 1 TO 3 DO BEGIN
Again, the outer loop
FOR K:= J TO 1 DO BEGIN
will be executed 3 times.
write('*')
The inner one will be
END;
entered 1 time for J = 1,
writeln
0 times for J = 2,
END
0 times for J = 3.
Therefore write will be called
1 time( 1 + 0 + 0 ).
Writeln will be called 3 times
Problem 2 (10 points)
How many times would the write beginning in the
following statements be executed? If the loop is invalid,
write invalid. and give the reason.
C)
FOR J:= 4 TO 6 DO BEGIN
FOR J:= 1 TO 5 DO BEGIN
write('*')
END;
writeln
END
Problem 2 (10 points)
How many times would the write beginning in the
following statements be executed? If the loop is invalid,
write invalid. and give the reason.
C)
FOR J:= 4 TO 6 DO BEGIN The trick here is that both
FOR J:= 1 TO 5 DO BEGIN loops have J as a counter.
write('*')
Be super-careful!
END;
Outer loop starts with J=4,
writeln
we go into inner one. J is reset to 1 and
END
inner loop runs from 1 to 5. Thus after we
leave the inner loop for the first time, J = 5! Forloop autoincrementing will increment J to 6, then we
enter the inner loop again, where J gets reset to 1 and
the inner loop runs from 1 to 5. The J is 5 again, again
it is incremented to 6 and the entire things repeats!
Infinite loop!
Problem 3 (10 points)
Indicate whether each of the following is valid or not. By
valid we mean, whether it is executable code that can
occur anywhere in a program. If it is not valid, explain
why not. Note that a variable can be of any type
a) True AND True
Problem 3 (10 points)
Indicate whether each of the following is valid or not. By
valid we mean, whether it is executable code that can
occur anywhere in a program. If it is not valid, explain
why not. Note that a variable can be of any type
a) True AND True
Yes, although it is quite silly :)
Problem 3 (10 points)
Indicate whether each of the following is valid or not. By
valid we mean, whether it is executable code that can
occur anywhere in a program. If it is not valid, explain
why not. Note that a variable can be of any type
b) CASE Character OF
'a': writeln('one');
'2': writeln('Two');
'3': writeln('Three')
END{CASE};
Problem 3 (10 points)
Indicate whether each of the following is valid or not. By
valid we mean, whether it is executable code that can
occur anywhere in a program. If it is not valid, explain
why not. Note that a variable can be of any type
b) CASE Character OF
'a': writeln('one');
'2': writeln('Two');
'3': writeln('Three')
END{CASE};
Sure. One good looking CASE statement.
Problem 3 (10 points)
Indicate whether each of the following is valid or not. By
valid we mean, whether it is executable code that can
occur anywhere in a program. If it is not valid, explain
why not. Note that a variable can be of any type
C) One OR Two AND Three
Problem 3 (10 points)
Indicate whether each of the following is valid or not. By
valid we mean, whether it is executable code that can
occur anywhere in a program. If it is not valid, explain
why not. Note that a variable can be of any type
C) One OR Two AND Three
Yes. The variables One, Two and Three have to
be of boolean type.
Problem 3 (10 points)
Indicate whether each of the following is valid or not. By
valid we mean, whether it is executable code that can
occur anywhere in a program. If it is not valid, explain
why not. Note that a variable can be of any type
D) 5 > ‘4’
Problem 3 (10 points)
Indicate whether each of the following is valid or not. By
valid we mean, whether it is executable code that can
occur anywhere in a program. If it is not valid, explain
why not. Note that a variable can be of any type
D) 5 > ‘4’
Can’t be. Types mismatch.
Problem 3 (10 points)
Indicate whether each of the following is valid or not. By
valid we mean, whether it is executable code that can
occur anywhere in a program. If it is not valid, explain
why not. Note that a variable can be of any type
E) if x := 4 then writeln(‘ow’);
Problem 3 (10 points)
Indicate whether each of the following is valid or not. By
valid we mean, whether it is executable code that can
occur anywhere in a program. If it is not valid, explain
why not. Note that a variable can be of any type
E) if x := 4 then writeln(‘ow’);
Nope. If expects a boolean expression.
Problem 4 (5 points)
(5 points) Complete the program segment that adds the odd
numbers from 1 to N, where N is read into the program. So if N
is 8, then the program would add 1, 3, 5, 7.
writeln('enter your number');
---------------Sum := _____
FOR J:= 1 TO ______ DO
IF _______________________then
Sum:=_________________
Problem 4 (5 points)
(5 points) Complete the program segment that adds the odd
numbers from 1 to N, where N is read into the program. So if N
is 8, then the program would add 1, 3, 5, 7.
writeln('enter your number');
---------------Sum := 0;
FOR J:= 1 TO _N_ DO
IF ( J MOD 2 = 1 ) then
Sum:= Sum + J;
Problem 5 (5 points)
5. (5 points) Complete the program segment that prints
the value of the variable letter, if letter is a capital
vowel. The vowels are (A, E, I, O, or U).
IF letter_____________________then
_________________
Problem 5 (5 points)
5. (5 points) Complete the program segment that prints
the value of the variable letter, if letter is a capital
vowel. The vowels are (A, E, I, O, or U).
IF letter in [‘A’, ‘E’, ‘I’, ‘O’, ‘U’ ] then
writeln( letter );
Note: we didn’t cover sets, so we could answer this with
either CASE statement or IF-STATEMENT
Problem 6 (10 points)
Complete the program segment that reads a group of numbers ending with
sentinel of -9 (a sentinel is the number or character that indicates the
end of the data) and places the even numbers in an array called A. For
instance, if the input were: 12 13 43 6 16 -9, the
program would place 12 in A[1], 6 in A[2] and 16 in A[3].
VAR j, number:integer;
A: ARRAY[1..100] OF integer;
BEGIN
writeln('type your numbers');
read(number);
j:=________
WHILE number <> -9 DO BEGIN
IF __________________________THEN
BEGIN
j:=________
A[____]:= Number;
________________
END
END
Problem 6 (10 points)
VAR j, number:integer;
A: ARRAY[1..100] OF integer;
BEGIN
writeln('type your numbers');
read(number);
j:=0;
WHILE number <> -9 DO BEGIN
IF ( number mod 2 = 0 ) THEN { Test if even }
BEGIN
j:=j+1;
{ Point to next array position }
A[ j ]:= Number;
read( number );
{ Read next number }
END
END
Problem 7 (10 points)
What does the following program produce?
program pattern;
const star = '*';
VAR j:integer;
BEGIN
for j:= 4 downto 1 do
writeln(star:j, star:10 - (2 * j) );
for j:= 1 to 4 do
writeln(star:j, star:10 - (2 * j) );
END.
Problem 7 (10 points)
program pattern;
const star = '*';
VAR j:integer;
1234567890
BEGIN
* *
for j:= 4 downto 1 do
*
*
writeln(star:j, star:10 - (2 * j) );
*
*
for j:= 1 to 4 do
*
*
writeln(star:j, star:10 - (2 * j) ); *
*
END.
*
*
*
*
* *
Problem 8 (10 points)
****
++++
***
+++
**
++
Complete the program that produces the pattern:
for j:=__________________DO
begin
________
________
end
Problem 8 (10 points)
Given the following procedures:
****
++++
procedure star(number:integer); ***
var j:integer;
+++
begin
**
for j:= 1 to number Do
++
write('*');
writeln
Complete the program that produces the
pattern:
end;
procedure plus(number:integer);
var j:integer;
begin
for j:= 1 to number Do
write('+');
writeln
end;
your goal is to produce the
following pattern:
for j:=__________________DO
begin
________
________
end
Problem 8 (10 points)
Given the following procedures:
****
++++
procedure star(number:integer); ***
var j:integer;
+++
begin
**
for j:= 1 to number Do
++
write('*');
writeln
Complete the program that produces the
pattern:
end;
procedure plus(number:integer);
var j:integer;
begin
for j:= 1 to number Do
write('+');
writeln
end;
your goal is to produce the
following pattern:
for j:= 4 DOWNTO 2 DO
begin
star( j );
plus( j );
end
Problem 9 (10 points)
Given the following heading:
procedure pattern(number: integer; symbol:char);
complete the procedure that when activated by, for instance,
pattern(5, '*'), would produce *****
and when activated by, for instance, pattern(3, '-') would produce --procedure pattern(number:integer; symbol:char);
VAR j:integer;
BEGIN
__________________
BEGIN
________________
END
END;
Problem 9 (10 points)
Given the following heading:
procedure pattern(number: integer; symbol:char);
complete the procedure that when activated by, for instance,
pattern(5, '*'), would produce *****
and when activated by, for instance, pattern(3, '-') would produce --procedure pattern(number:integer; symbol:char);
VAR j:integer;
BEGIN
for J:= 1 to number do
BEGIN
write( symbol );
END
END;
Problem 10 (20 points, do either
A or B)
A. Write a program that reads a sentence at least four
characters long into an array of characters
and prints every thing but the last three characters. The
sentence must end with an asterisk. Thus if the
sentence was hello there*, the program would print:
hello the as output. In other words, the re* would be
stored in the array but would not be
printed.
Problem 10 (20 points, do either
A or B)
B. Write a program that reads a sentence that ends with a
period, for instance, hello there.
and prints the sentence with each letter e replaced with
an asterisk. Thus in our example the
program would print h*llo th*r*.
Optional problems on arrays
Optional problems: page 473 #1, 2, 6, 13, 15
Problem 1
program t;
var i : integer;
x : array[1..5] of integer;
begin
for i:= 1 to 5 do
x[i] := 2*i;
for i:=1 to 5 do
{ Init every element of array to be 2*index }
{ If index less than three modify in one way
x[i] := 2*x[i] - x[i+2] else in another }
if ( i < 3 ) then
else
x[i] := -x[i];
for i:=1 to 5 do
writeln( x[ i ] );
end.
{ Just print elements }
-2, 0, -6, -8, -10 all on separate lines.
Problem 2
program prob2;
type Vector = array[ 1..10 ] of integer;
var Ray, L : Vector;
j : integer;
procedure box( M : Vector; VAR N : Vector );
var k : integer;
begin
for k:=1 to 10 do
N[ k ] := M[ k ] + k*k; { M[k] has squares of indexes, and we are adding squares of
end; { of procedure Box } indexes, so we will have 2*index^2 sitting in the N (or Ray) }
begin { Main }
for j := 1 to 10 do
L[ j ] := j*j;
{ Init L to be index squared: 1, 4, 9, etc. }
Box( L, Ray );
{ Note that Ray is passed by reference }
for j := 1 to 10 do
writeln( 'j = ',j, ' Ray = ', Ray[ j ] ); 2, 8, 18, 32, 50, 72, …, 200
end.
Problem 6
Write a program that reads ages of up to 100
people and prints the number of people who
are older than average and the number of
people who are younger than average.
Problem 13
Write program that determines the largest
element in an array X, and the value of its
subscript, given
VAR X : array[1..10] of integer;
Problem 15
Write a program that determines whether two
(integer) arrays of the same size have the
same elements.
GOOD LUCK ON ALL OF
YOUR FINALS
HAVE FUN
(IN GENERAL)
Programs from this lecture
Prob 10a from last year final
Prob 10b from last year final
Prob1 after chapter 10
Prob2 after chapter 10
Prob6 after chapter 10
Prob13 after chapter 10
Prob15 after chapter 10