Cant obtain a correct answer it sums incorectly and multiplicates too, i must use repeat when solving this problem, i suppose the problem is in sum:=i+i but i dont know how to solve it
program SAD;
uses crt;
var a, i, sum, prod: integer;
begin
clrscr;
sum:=0;
prod:=0;
{Sum}
repeat
for i:=1 to 26 do
if i mod 4 = 0 then sum:=i+i;
until i = 26;
{Multiplication}
repeat
for a:=1 to 26 do
if a mod 4 = 0 then prod:=a*a;
until a = 26;
writeln('Suma numerelor divizate la 4 este:', sum);
writeln('Produsul numerelor divizate la 4 este:', prod);
end.
I think the instruction "use repeat" probably intends that you should avoid using for as well.
There are a few errors in your code:
In the sum loop, you should add i to sum, not to itself.
In the prod loop, since you set prod to zero at the start, it will stay as zero because zero times anything is zero. So you need to adjust the logic of your prod calculation so that if prod is zero, when the mod 4 condition is satisfied, you set prod to the current value of a, otherwise you multiply it by a.
Here is some code which fixes the above points and avoids the use of for.
program Sad;
uses crt;
var
a, i, sum, prod: integer;
begin
clrscr;
sum:=0;
prod:=0;
{Sum}
i := 0;
repeat
inc(i);
if (i mod 4) = 0 then
sum := sum + i;
until i = 26;
{Multiplication}
a :=0;
repeat
inc(a);
if a mod 4 = 0 then begin
if prod = 0 then
prod := a
else
prod := prod * a;
end;
until a = 26;
writeln('Suma numerelor divizate la 4 este:', sum);
writeln('Produsul numerelor divizate la 4 este:', prod);
readln;
end.
Related
I have a program that reads a N number of integers and push them into an array, then I need to multiply the odd numbers from the array.
Program p2;
type
tab = array[1..10] of integer;
var
a, c : tab;
n, i, prod : integer;
begin
writeln('n=');
readln(n);
prod := 1;
writeln('Enter array numbers:');
for i := 1 to n do
read(a[i]);
if (a[i] mod 2 = 1) then
prod := a[i] * prod;
writeln('The produs of the odd numbers is: ',prod);
end.
For example when you enter the n as 5, and the numbers: 1, 2, 3, 4, 5;
The result of multiplication of odd numbers should be 15. Can someone help me to fix it working properly.
First off, whitespace and indentation are not terribly significant in Pascal, but they can be your ally in understanding what your program is doing, so let's make your code easier to read.
Program p2;
type
tab = array[1..10] of integer;
var
a, c : tab;
n, i, prod : integer;
begin
writeln('n=');
readln(n);
prod := 1;
writeln('Enter array numbers:');
for i := 1 to n do
read(a[i]);
if a[i] mod 2 = 1 then
prod := a[i] * prod;
writeln('The produs of the odd numbers is: ', prod);
end.
With indentation, it should be apparent what's happening. Your conditional only runs once, rather than each time through your loop. As suggested in the comments, begin and end neatly solve this problem by creating a block where the conditional is checked each time the loop runs.
program p2;
type
tab = array[1 .. 10] of integer;
var
a, c : tab;
n, i, prod : integer;
begin
writeln('n=');
readln(n);
prod := 1;
writeln('Enter array numbers:');
for i := 1 to n do
begin
read(a[i]);
if a[i] mod 2 = 1 then
prod := a[i] * prod;
end;
writeln('The produs of the odd numbers is: ', prod);
end.
I'm trying to teach myself Pascal, and am putting together a program to determine prime numbers. It's crude, and inaccurate, but just a practice exercise.
I've created a FOR loop that will see if a counted number has a remainder if divided by a set of prime numbers. If it doesn't it's not considered prime:
begin
writeln('This program calculates all the integers below a given number');
writeln('Please enter a number greater than 1');
readln(number);
//Need code to deal with entries that equal 1 or less, or aren't integers
prime:=true;
if number >=2 then writeln(2);
if number >=3 then writeln(3);
if number >=5 then writeln(5);
if number >11 then writeln(7);
For count := 1 to number do
begin
if count MOD 2 = 0 then prime:=false;
if count MOD 3 = 0 then prime:=false;
if count MOD 5 = 0 then prime:=false;
if count MOD 7 = 0 then prime:=false;
if prime = true then writeln(count);
writeln ('count= ',count)
end;
writeln('Hit any key to continue');
readln();
end.
However, no matter what number I put in, the For loop prints 1 for the prime number. I've added a count print to see if the loop is working, and it seems to be. Any tips?
Thanks in advance!
Your variable prime is set to true before entering the loop.
Inside the loop, when count is 1, the prime variable is not set again, hence it will print true.
In other words:
1 mod 2 equals 1
1 mod 3 equals 1
1 mod 5 equals 1
1 mod 7 equals 1
Since neither of these statements equals zero, the prime variable is not changed from its initial true value.
If you want to test if a number is a prime using a list of prime numbers, you should iterate from the list of prime numbers.
Here is a simple test that does that.
procedure TestIsPrime( number : Integer);
const
// A loopup table with primes. Expand to cover a larger range.
primes : array[1..4] of Integer = (2,3,5,7);
var
count : Integer;
highTest : Integer;
IsPrime : Boolean;
begin
if (number <= 0) then begin
WriteLn('Illegal number: ',number);
Exit;
end;
IsPrime := number > 1; // 1 is a special case !!
if (number >= Sqr(primes[High(primes)])) then begin
WriteLn('Needs more primes in table to test: ',number);
Exit;
end;
highTest := Trunc(Sqrt(number)); // Highest number to test
for count := 1 to High(primes) do begin
if (highTest >= primes[count]) then begin
if (number MOD primes[count] = 0) then begin
IsPrime := false;
Break;
end;
end
else
Break;
end;
if IsPrime = true then WriteLn(number);
end;
I've beeng having some trouble with this code... I need to create an algorithm which makes the user input a number (X), and then the program calculates the sum of all the odd numbers below (x).
This what I've tried so far, but can't really wrap my head around the logic behind it:
Program odd_numbers;
Var
Num, Limite, Soma: integer;
Begin;
Soma := 0;
Writeln('Choose a limit:');
Readln(Limite);
While (Limite / 2 > 0) do
Begin;
Soma := ((Num < Limite) mod 2 > 0);
Writeln('The sum of odd numbers from 0 to ', Limite, ' é ', Soma);
End;
if (Limite mod 2 = 0) then
Begin;
Soma := ((Num < Limite) mod 2 = 0);
Writeln('The sum of odd numbers from 0 to ', Limite, ' é ', Soma);
End;
End.
*PS: Been writing the code with variables in Portuguese, so don't mind the variables appearing weird to understand. *
I see that everyone is happily looping, but this is not necessary. This is a simple arithmetic sequence, and the sum can be calculated without a loop.
Just think of the following:
1 + 3 = 2 * (1 + 3) / 2 = 2 * 2 = 4 ; limits 3 and 4
1 + 3 + 5 = 3 * (1 + 5) / 2 = 3 * 3 = 9 ; limits 5 and 6
1 + 3 + 5 + 7 = 4 * (1 + 7) / 2 = 4 * 4 = 16 ; limits 7 and 8
1 + 3 + 5 + 7 + 9 = 5 * (1 + 9) / 2 = 5 * 5 = 25 ; limits 9 and 10
1 + 3 + 5 + 7 + 9 + 11 = 6 * (1 + 11) / 2 = 6 * 6 = 36 ; limits 11 and 12
But not only that, you'll see that it is in fact always a perfect square: Sqr((n+1) div 2).
So just calculate:
program odd_numbers;
var
Num, Limite, Soma: Integer;
begin
Write('Choose a limit: ');
Readln(Limite);
Num := (Limite + 1) div 2;
Soma := Num * Num;
Writeln('The sum of odd numbers from 0 to ', Limite, ' is ', Soma);
end.
Looks a little simpler than what the others propose.
The loop While (Limite / 2 > 0) do ... uses real arithmetic and not integer arithmetic. I guess you mean While (Limite div 2 > 0) do ... And you should change Limite in the loop otherwise you get stuck because the exit condition can never be reached.
After you have asked the user to enter a number, Limite, you need to keep that unchanged, because you need it in the final message. You also need a loop where you go through all numbers from Limite towards 0.
You started with a while loop which is ok, you are just missing the loop control variable. That is a variable that eventually gets a terminating value which then stops the loop. Use for example the Num variable you already have declared. You can use the same variable to investigate the numbers between user input and 0, for being odd values.
num := limite-1; // give num a start value based on user input (-1 because of "... numbers below (x)")
while num > 0 do // stop the loop when 0 is reached
begin
// here you investigate if `num` is a odd number (e.g. using `mod` operator or
// possibly your pascal has a built in `function Odd(value: integer): boolean;`)
// and add it to `Soma` if it is
num := num - 1;// decrement num at every iteration
end;
Finally you need to consider changes to the above, to handle negative input from the user.
To test if an integer is an odd value, you could use following function:
function IsOdd( value : Integer) : Boolean;
begin
IsOdd := (value mod 2) <> 0;
end;
Many pascal compilers have a built-in function called Odd(), which you could use.
A while loop works well to solve this problem. If you start with lowest odd number above zero, i.e. one and continue upwards so long we do not exceed the limit value we have a simple start:
function GetOddSumBelowX( X : Integer) : Integer;
var
i,sum: Integer;
begin
i := 1; // Start with first odd number
sum := 0;
while (i < X) do begin // as long as i less than X, loop
if IsOdd(i) then begin
sum := sum + i; // add to sum
end;
i := i + 1; // Increment i
end;
GetOddSumBelowX := sum;
end;
Now, that was simple enough. Next step to simplify the loop is to increment the i variable by two instead, just to jump between all odd numbers:
function GetOddSumBelowX( X : Integer) : Integer;
var
i,sum: Integer;
begin
i := 1; // Start with first odd number
sum := 0;
while (i < X) do begin // as long as i less than X, loop
sum := sum + i; // add to sum
i := i + 2; // Increment to next odd number
end;
GetOddSumBelowX := sum;
end;
Part of the program I have checks if an input number is a perfect number. We're supposed to find a solution that runs in O(sqrt(n)). The rest of my program runs in constant time, but this function is holding me back.
function Perfect(x: integer): boolean;
var
i: integer;
sum: integer=0;
begin
for i := 1 to x-1 do
if (x mod i = 0) then
sum := sum + i;
if sum = x then
exit(true)
else
exit(false);
end;
This runs in O(n) time, and I need to cut it down to O(sqrt(n)) time.
These are the options I've come up with:
(1) Find a way to make the for loop go from 1 to sqrt(x)...
(2) Find a way to check for a perfect number that doesn't use a for loop...
Any suggestions? I appreciate any hints, tips, instruction, etc. :)
You need to iterate the cycle not for i := 1 to x-1 but for i := 2 to trunc(sqrt(x)).
The highest integer divisor is x but we do not take it in into account when looking for perfect numbers. We increment sum by 1 instead (or initialize it with 1 - not 0).
The code if (x mod i = 0) then sum := sum + i; for this purpose can be converted to:
if (x mod i = 0) then
begin
sum := sum + i;
sum := sum + (x div i);
end;
And so we get the following code:
function Perfect(x: integer): boolean;
var
i: integer;
sum: integer = 1;
sqrtx: integer;
begin
sqrtx := trunc(sqrt(x));
i := 2;
while i <= sqrtx do
begin
if (x mod i = 0) then
begin
sum := sum + i;
sum := sum + (x div i) // you can also compare i and x div i
//to avoid adding the same number twice
//for example when x = 4 both 2 and 4 div 2 will be added
end;
inc(i);
end;
if sum = x then
exit(true)
else
exit(false);
end;
You play a game with 100 opponents. The game has k rounds. Every round you can eliminate some opponents (always atleast 1). You are rewarded for eliminating them.
The reward is: 100.000 * '# of eliminated opponents' / '# of opponents' <= in integers (rounded down)
I want to eliminate the opponents in a way, that gets me the largest amount of money possible.
Example game:
number of rounds = 3
first round we eliminate 50 opponents, so we get 100.000 * 50 / 100 = +50.000
second round we eliminate 30, so we get 100.000 * 30 / 50 = +60.000
last round we eliminate last 20 opponents, so we get 100.000 * 20 / 20 = +100.000
so the total winnings are: 210.000
I tried to write up something, but I don't think it's the most effective way to do it?
Program EliminationGame;
var
selectedHistory : array [1..10] of integer;
opponentCount,roundCount : integer;
maxOpponents,numberSelected : integer;
totalMoney : integer;
i : integer;
begin
totalMoney := 0;
maxOpponents := 100;
opponentCount := maxOpponents;
roundCount := 3; {test value}
for i:=1 to roundCount do begin
if (i = roundCount) then begin
numberSelected := opponentCount;
end else begin
numberSelected := floor(opponentCount / roundCount);
end;
selectedHistory[i] := numberSelected;
totalMoney := floor(totalMoney + (numberSelected / opponentCount * 100000));
opponentCount := opponentCount - numberSelected;
end;
writeln('Total money won:');
writeln(totalMoney);
writeln('Amount selected in rounds:');
for i:= 0 to Length(selectedHistory) do
write(selectedHistory[i],' ');
end.
Also it seems that floor function does not exist in pascal?
It seems the question has a maths answer that can be calculated in advance. As #Anton said it was obvious that the number of points given during the third round did not depend upon the number of eliminated enemies. So the third round should eliminate 1 enemy.
So We get the following function for a thre-round game.
f(x)=100000x/100+100000(99-x)/(100-x)+100000*1/1, where x- the number
of enemies eleminated at first round.
if we find the extrema (local maximum of the function) it appears equal to 90. That means the decision is the following: the first round eliminates 90 the second - 9, the third - 1 enemy.
Of course, for consideration: 90=100-sqrt(100).
In other words: the Pascal decision of the task is to loop a variable from 1 to 99 and see the maximum of this function. X-will be the answer.
program Project1;
var
x, xmax: byte;
MaxRes, tmp: real;
begin
xmax := 0;
MaxRes := 0;
for x := 1 to 99 do
begin
tmp := 100000 * x / 100 + 100000*(99 - x) / (100 - x) + 100000 * 1 / 1;
if tmp > MaxRes then
begin
MaxRes := tmp;
xmax := x;
end;
end;
writeln(xmax);
readln;
end.
The general decision for other number of enemies and rounds (using recursion) is the following (Delphi dialect):
program Project1;
{$APPTYPE CONSOLE}
{$R *.res}
Uses System.SysUtils;
var
s: string;
function Part(RemainingEnemies: byte; Depth: byte;
var OutputString: string): real;
var
i: byte;
tmp, MaxRes: real;
imax: byte;
DaughterString: string;
begin
OutputString := '';
if Depth = 0 then
exit(0);
imax := 0;
MaxRes := 0;
for i := 1 to RemainingEnemies - Depth + 1 do
begin
tmp := i / RemainingEnemies * 100000 + Part(RemainingEnemies - i, Depth - 1,
DaughterString);
if tmp > MaxRes then
begin
MaxRes := tmp;
imax := i;
OutputString := inttostr(imax) + ' ' + DaughterString;
end;
end;
result := MaxRes;
end;
begin
writeln(Part(100, 3, s):10:1);//first parameter-Enemies count,
//2-Number of rounds,
//3-output for eliminated enemies counter
writeln(s);
readln;
end.
This problem can be solved with a dynamic approach.
F(round,number_of_opponents_remained):
res = 0
opp // number_of_opponents_remained
for i in [1 opp]
res = max(res, opp/100 + F(round-1,opp - i) )
return res
I should say this not the complete solution and you add some details about it, and I am just giving you an idea. You should add some details such as base case and checking if opp>0 and some other details. The complexity of this algorithm is O(100*k).