## 913 - Joana and the Odd Numbers

All about problems in Volume 9. If there is a thread about your problem, please use it. If not, create one with its number in the subject.

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sakhassan
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### 913 - Joana and the Odd Numbers

Do i need to precalculate??
how i determine the 1st integer of the line N ????

Jan
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No need to precalculate anything. You can find a general formula to find the last integer in the line N. First list all the numbers -

Line 1 - 1
Line 3 - 7
Line 5 - 17
Line 7 - 31
Line 9 - 49
Line 11 - 71
...
Line N - ?

The formula is not so tough. Try it.
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sakhassan
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Thanks J@N.... I got the formula

kana
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can anyone tell me whats the wrong with my code?
Last edited by kana on Tue Nov 28, 2006 9:54 pm, edited 1 time in total.

Jan
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Try the samples

Input:

Code: Select all

``````99999999
1000000001``````
Output:

Code: Select all

``````14999999999999991
1500000005999999997``````
Use 'long long' istead of 'long double'. Dont forget to remove your code. And remember that if you want to post a code then paste your code using 'code' from the editor. Hope these help.
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Iffat
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### 913...TLE!!!!

can anyone expain why i am getting TLE for this code

Code: Select all

``````CUT
``````
plzzzzzzzzzz help me!!!
thanx
Last edited by Iffat on Mon Dec 04, 2006 1:17 pm, edited 1 time in total.

Jan
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Read the previous posts and run your code with those samples. You will find the reason yourself.
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Iffat
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thanx for reply..but i am still confused ...i used long long...will u explain my bug plzz?

Jan
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'long long' is not the problem.

Code: Select all

``````      while(n!=1)
{
sum=sum+(n*2);
n-=2;
}  ``````
If the value of 'n' is big, like 1000000001, then you have to use this loop for (1000000001/2) times. Which is too big. Try to figure out the last odd number in a certain line. You dont have to use any loop. You can find a general formula. Then the result can be found in just O(1) time, which means no loop. Hope you can generate the formula.
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Iffat
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thanx jan i got the formula and got AC

rezaeeEE
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### why wa?

Code: Select all

``````removed after accept
``````
Last edited by rezaeeEE on Thu May 24, 2007 9:54 pm, edited 1 time in total.

Jan
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functoin pow() returns double, and you are assigning it to a 'long long' variable. So, precision problems can occur easily. Try to get rid of floating point calculations.
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rezaeeEE
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### thank u

thank u very much mr jan.
you are a great helper.

laicc86
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Code: Select all

``````deleted after AC
``````
i get RE for this...can anyone help me? thx
Last edited by laicc86 on Thu Oct 25, 2007 6:59 pm, edited 1 time in total.

Jan
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The input set contains valid cases. So, no need to check n. And the function should be

Code: Select all

``long long odd_num(long long num)``
Hope these help.
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