how to?

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Dear programmer and engineers.
Please help me how to programe this in python.

should print like this.

>>> 1-2+3=2

Thanks in advance.

alece

· Snapshot 141

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like this ?

print (1-2+3)

question clear bhayena bro!! ^^

chi-sigma

· Snapshot 166

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do you mean this?

print "1-2+3=",1-2+3

comingsoon

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I try this but total is not right.
also 1-2+3-4 doesn't work while user give odd number.

N = int(input("N: "))
i=1
x=2
Sum1=0
Sum2=0
while i <= N and x <=N:
    print("+", i, "-", x, end=' ')
    i= i+2
    x= x+2
    Sum1=Sum1+i
    Sum2=Sum2+x
print("=", Sum1-Sum2)

Result
>>>
N: 4
+ 1 - 2 + 3 - 4 = -2

>>> ================================ RESTART ================================
>>>
N: 5
+ 1 - 2 + 3 - 4 = -2
>>>
Here it prints only 4, should print upto 5(user's given value) and total is not valid.

Last edited: 06-Feb-13 12:50 PM

Kiddo

· Snapshot 332

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You have a flaw in your logic

I am not familiar with Python programming and am no longer a programmer, but it seems fairly straight forward so I tested your logic and you are getting what you are programming.

Flaw

First of all, how can you print two variables at a time (i and x with print function) when you might have to print odd number of variables (say N=5)? WIth you program you can only do 1-2+3-4+5-6 and so on, not 1-2+3 OR 1-2+3-4+5.
Second, for N=5, your program will NOT run beyond those 4 since X becomes 6 which stops the program from going more than 2 iterations, hence 4 values.

Let's check it out (for N=5)

First iteration: x (initial value) = 2, x (final value)=4 //Since x=x+2

Second iteration: x (initial value) = 4, x (final value)=6

Third iteration fails as x>N

Solution

First of all, you can't print two variables at once since you can have odd number of digits (like N=5).

But, if you print one at a time, you have to alternate between + and -.
You can do this in a number of ways, let's keep it simple and use i as our counter. So if i is odd (i/2 not=1) then you will print "-" and add to the sum while if it is even you will do opposite:

N = int(input("N: "))
i=1
Sum=0

while i <= N:

    if i/2=1:                                             //If i is even
           print(i, "+", end=' ')
           Sum=Sum-i
    else:                                                  //if i is odd
           print(i, "-", end=' ')
           Sum=Sum+i

i=i+1

print("=", Sum)

Like I said, I am not familiar with Python and might have my syntax wrong, but the logic should work.

comingsoon

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Thanks kiddo, I'm now almost in the solutin. there is little thing to correct.
Code:

N = int(input("N: "))
i=1
Sum1=0
Sum2=0

while i <= N:

    if i%2==0:                                              #If i is even
           print("-",i, end=' ')
           Sum1=Sum1+i
    else:                                                  #if i is odd
           print("+", i, end=' ')
           Sum2=Sum2+i
    i=i+1

print("=", Sum2-Sum1)

Result:
N: 5
+ 1 - 2 + 3 - 4 + 5 = 3
>>> ================================ RESTART ================================
>>>
N: 3
+ 1 - 2 + 3 = 2
>>> ================================ RESTART ================================
>>>
N: 4
+ 1 - 2 + 3 - 4 = -2

How to remove + sign before 1
should look like this
1-2+3-4=-2

comingsoon

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Thanks everyone, specially thanks kiddo for your help.
I got a solution printing 1 before the loop and starting counter i=2, But I feel like very Tori Method

.
if someone have different idea please suggest me, I wanna learn.

prankster

· Snapshot 398

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N = int(input("N: "))
i=1
Sum=0

while i <= N:

    if i%2==0:
if (i !=1)
print("-") #If i is even
           print(i)

           Sum=Sum-i
    else:
  if (i !=1)
print("+")                                               #if i is odd
           print(i)
Sum=Sum+i
    i=i+1

print("=", Sum)

Last edited: 06-Feb-13 03:56 PM

Kiddo

· Snapshot 398

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While changing the syntax (i%2 instead of i/2) is understandable, I don't know why you changed the logic? If you keep my logic intact, you should get it the way you want it, i.e 1-2+3-4+5=3

N = int(input("N: "))
i=1
Sum=0

while i <= N:

    if i%2==0:                                              #If i is even
           print(i, "+", end=' ')
           Sum=Sum-i
    else:                                                  #if i is odd
           print(i, "-", end=' ')
           Sum=Sum+i
    i=i+1

print("=", Sum)

prankster

· Snapshot 437

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@Kiddo, just wondering won't urs result into
1-2+3-4+5-=3

comingsoon

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Sorry kiddo, there was some syntax error so I modifed and came to my way. I am using python 3.2.3.
There is extra sign at last of the series.
Here is result of your last code.
N: 5
1 - 2 + 3 - 4 + 5 - = 3
>>> ================================ RESTART ================================
>>>
N: 4
1 - 2 + 3 - 4 + = -2
>>>

prankster,
your code don't render 1 at begining and series start from - sign, same problem as we discuss here. Here is the result.
>>> ================================ RESTART ================================
>>>
N: 5
-
2
+
3
-
4
+
5
= 2
>>> ================================ RESTART ================================
>>>
N: 4
-
2
+
3
-
4
= -3

prankster

· Snapshot 465

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I'm not familiar with python either, following if should only be for   print("-") and not print(i) . and i assume, end=' ' is for not adding line break.
if (i !=1)
print("-")

N = int(input("N: "))
i=1
Sum=0

while i <= N:

    if i%2==0:
if (i !=1):
print("-") #If i is even
           print(i)

           Sum=Sum-i
    else:
  if (i !=1):
print("+")                                               #if i is odd
           print(i)
Sum=Sum+i
    i=i+1

print("=", Sum)

probably that would work, pls add end = ' ' to all the print statement

magorkhe1

· Snapshot 481

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EDX.ORG has many online courses. MIT is offering Python and it started yesterday. Anybody interested can sign any time and any courses.

https://www.edx.org/

Kiddo

· Snapshot 510

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You both are right, it will have the sign at the end.
I am done for today and will look at it tomorrow in case prankster's doesn't work.

comingsoon

· Snapshot 523

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prankstar there is still same problem, I modefied little bit for syntax error here is result.
>>> ================================ RESTART ================================
>>>
N: 7
-
2
+
3
-
4
+
5
-
6
+
7
= 3
>>>

I'm not worried for same line but 1 is missing from begining. I am still try to modify if i can get that 1 on begining. Thanks

Last edited: 06-Feb-13 05:08 PM

prankster

· Snapshot 553

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did you put indentation for print(i)
print("-")
print(i)

I went to http://mathcs.holycross.edu/~kwalsh/python/
and tried following code,

N = 5

i=1

Sum=0

while i <= N:

if i%2==0:

if (i !=1):

print "-"