In the second approach I wrote to use array for mapping
> "you can simply map the existence/non-existence of any particular element
> in an array. that will be in constant time (for query purposes) and O(n)
> time for preprocessing."
>
> On Fri, May 27, 2011 at 2:18 AM, sukhmeet singh <sukhmeet2...@gmail.com>wrote:
> actly i did.. but bhavana didn;t used STL ..!!
> My question to you was regarding Dave 's query which i didn't understand
> what he meant by saying : "@Aakash: And tell me how map works. Is making an
> entry O(1) regardless
>
> of the value of the entry? For example, is it O(n) to map the sequence
> 1, 4, 9, 16, 25, ..., n^2? "
>
>
>
>
>
> On Fri, May 27, 2011 at 2:44 PM, Aakash Johari <aakashj....@gmail.com>wrote:
>
>> @sukhmeet: could you get my approach? it was same as Bhavana explained.
>>
>> On Fri, May 27, 2011 at 2:12 AM, bhavana <bhavana....@gmail.com> wrote:
>>
>>> hehe...d difference is regarding time complexity...bcoz map takes 0(logN)
>>> for insertion while array can b accessed in constant time through index.
>>>
>>>
>>> On Fri, May 27, 2011 at 2:39 PM, sukhmeet singh
>>> <sukhmeet2...@gmail.com>wrote:
>>>
>>>> k.. got it .. but it was same as putting them into a map ..if the bound
>>>> 'b' is not known.. as said be Akash ..
>>>> But if STL is not allowed your approach is mch better..Noogle..
>>>>
>>>> also a simple change that can be done if the each number is that we can
>>>> check if (sum - a[i] )!= i then getting same can be avoided
>>>>
>>>> On Fri, May 27, 2011 at 2:32 PM, bhavana <bhavana....@gmail.com> wrote:
>>>>
>>>>> hey...bt this one works only in case given that the elements of the
>>>>> array are non-negative.
>>>>>
>>>>>
>>>>> On Fri, May 27, 2011 at 2:30 PM, bhavana <bhavana....@gmail.com>wrote:
>>>>>
>>>>>> @sukhi : instead of using a map...use a boolean array elements of
>>>>>> whoch r initialised to false.
>>>>>>
>>>>>> Starting frm the first element of the array....if the number n is
>>>>>> greater than k ignore it....else mark a[n]=true and check if a[k-n]==true
>>>>>> then we get the required result .....bt if we reach the end of array
>>>>>> without
>>>>>> entering the if condition the array doesnt contain any such pair.
>>>>>>
>>>>>>
>>>>>> On Fri, May 27, 2011 at 2:26 PM, sukhmeet singh <
>>>>>> sukhmeet2...@gmail.com> wrote:
>>>>>>
>>>>>>> @bhavana : Explain..!!
>>>>>>> as far as i get you is that it would be same as implementing map
>>>>>>> ...!! isn't ??
>>>>>>>
>>>>>>>
>>>>>>> On Fri, May 27, 2011 at 2:16 PM, bhavana <bhavana....@gmail.com>wrote:
>>>>>>>
>>>>>>>> can be solved easily if the elements of the array lie in a limited
>>>>>>>> range which can b known beforehand...!!
>>>>>>>>
>>>>>>>>
>>>>>>>> On Fri, May 27, 2011 at 2:10 PM, Aakash Johari <
>>>>>>>> aakashj....@gmail.com> wrote:
>>>>>>>>
>>>>>>>>> yes, you are right. map insertion takes O(log n) time. so if you
>>>>>>>>> know the upper bound of N, you can simply map the
>>>>>>>>> existence/non-existence of
>>>>>>>>> any particular element in an array. that will be in constant time
>>>>>>>>> (for query
>>>>>>>>> purposes) and O(n) time for preprocessing.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Fri, May 27, 2011 at 1:29 AM, sukhmeet singh <
>>>>>>>>> sukhmeet2...@gmail.com> wrote:
>>>>>>>>>
>>>>>>>>>> @Dave nd @Akash can u explain a bit more.. I didn't get what u
>>>>>>>>>> say..
>>>>>>>>>> Inserting in a map takes O(log n) time !!
>>>>>>>>>>
>>>>>>>>>> On Fri, May 20, 2011 at 8:35 PM, Aakash Johari <
>>>>>>>>>> aakashj....@gmail.com> wrote:
>>>>>>>>>>
>>>>>>>>>>> @Dave: This is what is still a doubt to me. I have searched but
>>>>>>>>>>> couldn't get the info regarding this.
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> On Fri, May 20, 2011 at 8:01 AM, Dave
>>>>>>>>>>> <dave_and_da...@juno.com>wrote:
>>>>>>>>>>>
>>>>>>>>>>>> @Aakash: And tell me how map works. Is making an entry O(1)
>>>>>>>>>>>> regardless
>>>>>>>>>>>> of the value of the entry? For example, is it O(n) to map the
>>>>>>>>>>>> sequence
>>>>>>>>>>>> 1, 4, 9, 16, 25, ..., n^2?
>>>>>>>>>>>>
>>>>>>>>>>>> Dave
>>>>>>>>>>>>
>>>>>>>>>>>> On May 20, 9:39 am, Aakash Johari <aakashj....@gmail.com>
>>>>>>>>>>>> wrote:
>>>>>>>>>>>> > @Dave: I got you. I will have to check before pushing the
>>>>>>>>>>>> element in map.
>>>>>>>>>>>> >
>>>>>>>>>>>> >
>>>>>>>>>>>> >
>>>>>>>>>>>> >
>>>>>>>>>>>> >
>>>>>>>>>>>> > On Fri, May 20, 2011 at 7:30 AM, Dave <
>>>>>>>>>>>> dave_and_da...@juno.com> wrote:
>>>>>>>>>>>> > > @Aakash: Yeah, but try the same array with sum = 6 and see
>>>>>>>>>>>> what
>>>>>>>>>>>> > > happens.
>>>>>>>>>>>> >
>>>>>>>>>>>> > > Dave
>>>>>>>>>>>> >
>>>>>>>>>>>> > > On May 20, 9:04 am, Aakash Johari <aakashj....@gmail.com>
>>>>>>>>>>>> wrote:
>>>>>>>>>>>> > > > int main()
>>>>>>>>>>>> > > > {
>>>>>>>>>>>> > > > int a[10] = {5, 3, 10, 9, 8, 23, 11, 4, 12, 6};
>>>>>>>>>>>> > > > int i;
>>>>>>>>>>>> > > > int sum;
>>>>>>>>>>>> > > > int flag = 0;
>>>>>>>>>>>> >
>>>>>>>>>>>> > > > map<int, int> m;
>>>>>>>>>>>> >
>>>>>>>>>>>> > > > for ( i = 0; i < 10; i++ ) {
>>>>>>>>>>>> > > > m[a[i]] = 1;
>>>>>>>>>>>> > > > }
>>>>>>>>>>>> >
>>>>>>>>>>>> > > > sum = 13;
>>>>>>>>>>>> >
>>>>>>>>>>>> > > > for ( i = 0; i < 10; i++ ) {
>>>>>>>>>>>> > > > if ( m[sum - a[i]] == 1 ) {
>>>>>>>>>>>> > > > flag = 1;
>>>>>>>>>>>> > > > break;
>>>>>>>>>>>> > > > }
>>>>>>>>>>>> > > > }
>>>>>>>>>>>> >
>>>>>>>>>>>> > > > if ( flag == 1 )
>>>>>>>>>>>> > > > cout << a[i] << " " << sum - a[i] << endl;
>>>>>>>>>>>> >
>>>>>>>>>>>> > > > return 0;
>>>>>>>>>>>> >
>>>>>>>>>>>> > > > }
>>>>>>>>>>>> > > > On Fri, May 20, 2011 at 7:01 AM, hari <
>>>>>>>>>>>> rajakin...@gmail.com> wrote:
>>>>>>>>>>>> > > > > We can sort using STL sort function in main() before
>>>>>>>>>>>> function call of
>>>>>>>>>>>> > > > > arraysum().
>>>>>>>>>>>> >
>>>>>>>>>>>> > > > > On May 20, 6:49 am, Gunjan Sharma <
>>>>>>>>>>>> gunjan.khan...@gmail.com> wrote:
>>>>>>>>>>>> > > > > > First of all there is an infinite loop in this
>>>>>>>>>>>> code....
>>>>>>>>>>>> > > > > > Secondly it works only for sorted array.
>>>>>>>>>>>> >
>>>>>>>>>>>> > > > > > On Fri, May 20, 2011 at 7:16 PM, hari <
>>>>>>>>>>>> rajakin...@gmail.com> wrote:
>>>>>>>>>>>> > > > > > > In while loop have i,j which points first and last
>>>>>>>>>>>> index of array.
>>>>>>>>>>>> > > In
>>>>>>>>>>>> > > > > > > while loop, Check the sum of a[i],a[j], If
>>>>>>>>>>>> sum<k,increment i or
>>>>>>>>>>>> > > else
>>>>>>>>>>>> > > > > > > decrement j. Run the while loop till i<j..
>>>>>>>>>>>> >
>>>>>>>>>>>> > > > > > > CODE:
>>>>>>>>>>>> >
>>>>>>>>>>>> > > > > > > int arraysum(int a[], int k, int i, int j)
>>>>>>>>>>>> > > > > > > while(i<j)
>>>>>>>>>>>> > > > > > > {
>>>>>>>>>>>> > > > > > > int p=0;
>>>>>>>>>>>> > > > > > > int b[10]; //to store index of selected nos
>>>>>>>>>>>> > > > > > > sum=a[i]+a[j];
>>>>>>>>>>>> > > > > > > if (sum==k)
>>>>>>>>>>>> > > > > > > {
>>>>>>>>>>>> > > > > > > b[p++]=i;b[p++]=j;
>>>>>>>>>>>> > > > > > > }
>>>>>>>>>>>> > > > > > > elseif(sum<k)
>>>>>>>>>>>> > > > > > > i++;
>>>>>>>>>>>> > > > > > > else(sum>k)
>>>>>>>>>>>> > > > > > > j++;
>>>>>>>>>>>> > > > > > > return b;
>>>>>>>>>>>> > > > > > > }
>>>>>>>>>>>> >
>>>>>>>>>>>> > > > > > > On May 20, 4:38 am, amit <amitthecoo...@gmail.com>
>>>>>>>>>>>> wrote:
>>>>>>>>>>>> > > > > > > > given an array of integers, and an integer k, find
>>>>>>>>>>>> out two
>>>>>>>>>>>> > > elements
>>>>>>>>>>>> > > > > > > > from the array whose sum is k in O(n) time. if no
>>>>>>>>>>>> such element
>>>>>>>>>>>> > > exists
>>>>>>>>>>>> > > > > > > > output none.
>>>>>>>>>>>> >
>>>>>>>>>>>> > > > > > > --
>>>>>>>>>>>> > > > > > > You received this message because you are subscribed
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>>>>>>>>>>>> > > > > > > "Algorithm Geeks" group.
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>>>>>>>>>>>> > > > > > > To unsubscribe from this group, send email to
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>>>>>>>>>>>> >
>>>>>>>>>>>> > > > > > --
>>>>>>>>>>>> > > > > > Regards
>>>>>>>>>>>> > > > > > Gunjan Sharma
>>>>>>>>>>>> > > > > > B.Tech IV year CSE
>>>>>>>>>>>> >
>>>>>>>>>>>> > > > > > Contact No- +91 9997767077
>>>>>>>>>>>> >
>>>>>>>>>>>> > > > > --
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>>>>>>>>>>>> >
>>>>>>>>>>>> > > > --
>>>>>>>>>>>> > > > -Aakash Johari
>>>>>>>>>>>> > > > (IIIT Allahabad)- Hide quoted text -
>>>>>>>>>>>> >
>>>>>>>>>>>> > > > - Show quoted text -
>>>>>>>>>>>> >
>>>>>>>>>>>> > > --
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>>>>>>>>>>>> >
>>>>>>>>>>>> > --
>>>>>>>>>>>> > -Aakash Johari
>>>>>>>>>>>> > (IIIT Allahabad)- Hide quoted text -
>>>>>>>>>>>> >
>>>>>>>>>>>> > - Show quoted text -
>>>>>>>>>>>>
>>>>>>>>>>>> --
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>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> --
>>>>>>>>>>> -Aakash Johari
>>>>>>>>>>> (IIIT Allahabad)
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>> --
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>>>>>>>>>>
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>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> --
>>>>>>>>> -Aakash Johari
>>>>>>>>> (IIIT Allahabad)
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> --
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>>>>>>>>
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>>>>>>
>>>>>>
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>>
>>
>>
>> --
>> -Aakash Johari
>> (IIIT Allahabad)
>>
>>
>>
>>
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