913 - Joana and the Odd Numbers

[sakhassan]

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

[Jan]

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.

[sakhassan]

Thanks J@N.... I got the formula

[kana]

can anyone tell me whats the wrong with my code?

[Jan]

Try the samples

Input:

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99999999
1000000001

Output:

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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.

[Iffat]

can anyone expain why i am getting TLE for this code

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CUT


plzzzzzzzzzz help me!!!
thanx

[Jan]

Read the previous posts and run your code with those samples. You will find the reason yourself.

[Iffat]

thanx for reply..but i am still confused ...i used long long...will u explain my bug plzz?

[Jan]

'long long' is not the problem.

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      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.

[Iffat]

thanx jan i got the formula and got AC

[rezaeeEE]

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removed after accept


[Jan]

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.

[rezaeeEE]

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

[laicc86]

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deleted after AC


i get RE for this...can anyone help me? thx

[Jan]

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

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long long odd_num(long long num)

Hope these help.