Forums: » Register « |  Free Tools |  User CP |  Games |  Calendar |  Members |  FAQs |  Sitemap |  Support |
 User Name: Password: Remember me

New Free Tools on Dev Shed!
We're Excited to announce that Dev Shed now has 70 free tools on the site. To learn more, click here!

 Dev Shed Forums Sponsor:
#1
May 12th, 2006, 11:28 PM
 rani_techie
Registered User

Join Date: May 2006
Location: San Diego,CA
Posts: 2
Time spent in forums: 54 m 12 sec
Reputation Power: 0
Algorithm to find second largest element in an array

Hello friends,
I need to find second largest number in an array of n elements. I have tried a c code for that...

#include <stdio.h>
int main(void) {
int pri, sec, i, v;
int arr[] = {4,10,3,8,6,7,2,7,9,2,0};
pri = sec = 0;
for (i = 0; arr[i]; ++i) {
v = arr[i];
if (v > pri) sec = pri, pri = v;
if (v > sec && v < pri) sec = v;
}
printf("pri is %d, sec is %d\n", pri, sec);
return 0;
}

but i want to know how to find complexity of the algorithm in worst case. and is there any algorithm whose complexity is 2n-3 which cud do the same task?

thnx,
raniiii

#2
May 13th, 2006, 09:02 PM
 Lux Perpetua
Contributing User

Join Date: Feb 2004
Location: San Francisco Bay
Posts: 1,939
Time spent in forums: 1 Month 1 Week 3 h 27 m 29 sec
Reputation Power: 1312
If by "2n-3" you are referring to the number of comparisons, then yes: go through and find the largest element (n-1 comparisons), get it out of the way, and then go through and find the largest remaining element (n-2 comparisons).

As for analyzing worst-case complexity in an algorithm like this: the loop body does 3 comparisons and some number of assignments. In the worst case, you will do 3 assignments on each iteration (if the array is sorted). You do all of that n times, so you do 3n comparisons and 3n assignments in the worst case in the loop part of the code. Add to that the overhead for setting things up, initializing structures, etc.

#3
May 14th, 2006, 05:28 AM
 rani_techie
Registered User

Join Date: May 2006
Location: San Diego,CA
Posts: 2
Time spent in forums: 54 m 12 sec
Reputation Power: 0
thnx

thnx for the reply but in a for loop u consider 0(n) complexity no matter how many comparisons u make rite ?

#4
April 29th, 2009, 10:29 AM
 sandeep_patra
Registered User

Join Date: Apr 2009
Posts: 1
Time spent in forums: 7 m 53 sec
Reputation Power: 0
Hi rani,
u r correct in a loop what does matters is how many times it runs and not the number of comparisons inside it.

so for your algorithm the complexity is O(n) as the loop is running for n times.

now if u want to have an algorithm giving you O(2n -3). then we could think of bubble short to find the second largest element in the array.

ok the complexity of bubble sort is O(n^2) to short complete array of elements.
as we need the second largest number, so we can run the loop only 2 times.
in the first time loop will run for (n-1) times and second time it will run for (n -2).
So all total we have (n-1) + (n-2) = 2n -3.

bye,
Sandeep Patra

#5
August 29th, 2009, 03:35 PM
 sathish_leo
Registered User

Join Date: Aug 2009
Posts: 1
Time spent in forums: 2 m 10 sec
Reputation Power: 0
public void FindSec()
{
int[] arr = { 1,2,0,-1,8,26,1,26};
int high, secHigh, temp, i;

high = secHigh = arr[0];

for (i = 1; i < arr.Length; ++i)
{
temp = arr[i];
if(temp > high)
{
secHigh = high;
high = temp;
}
else if(temp >secHigh && temp != high)
{
secHigh = temp;
}
}

Console.WriteLine(secHigh);
}

#6
September 21st, 2010, 02:21 PM
 sssrit
Registered User

Join Date: Sep 2010
Posts: 1
Time spent in forums: 5 m 44 sec
Reputation Power: 0
Quote:
 Originally Posted by sathish_leo public void FindSec() { int[] arr = { 1,2,0,-1,8,26,1,26}; int high, secHigh, temp, i; high = secHigh = arr[0]; for (i = 1; i < arr.Length; ++i) { temp = arr[i]; if(temp > high) { secHigh = high; high = temp; } else if(temp >secHigh && temp != high) { secHigh = temp; } } Console.WriteLine(secHigh); }

I think this code will not work , when 1st element of the array will greatest elemnt .....

#7
October 13th, 2010, 02:37 PM
Registered User

Join Date: Oct 2010
Posts: 1
Time spent in forums: 7 m 41 sec
Reputation Power: 0
This method is incorrect,it will not run at these type of arrays exp: a={10,3,4}

Error
This method is incorrect,it will not run at these type of arrays exp: a={10,3,4}

Quote:
 Originally Posted by sathish_leo public void FindSec() { int[] arr = { 1,2,0,-1,8,26,1,26}; int high, secHigh, temp, i; high = secHigh = arr[0]; for (i = 1; i < arr.Length; ++i) { temp = arr[i]; if(temp > high) { secHigh = high; high = temp; } else if(temp >secHigh && temp != high) { secHigh = temp; } } Console.WriteLine(secHigh); }

 Viewing: Dev Shed Forums > Programming Languages - More > Software Design > Algorithm to find second largest element in an array

## Developer Shed Advertisers and Affiliates

 Thread Tools Search this Thread Search this Thread: Advanced Search Display Modes Rate This Thread Linear Mode Rate This Thread: 5 : Excellent 4 : Good 3 : Average 2 : Bad 1 : Terrible

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts vB code is On Smilies are On [IMG] code is On HTML code is Off
 View Your Warnings | New Posts | Latest News | Latest Threads | Shoutbox Forum Jump Please select one User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home -------------------- Programming Languages    PHP Development        PHP FAQs and Stickies    Perl Programming        Perl FAQs and Stickies    C Programming        C Programming FAQs and Stickies    Java Help        Java FAQs    Python Programming        Python Programming FAQs    Ruby Programming        Ruby Programming FAQs    Game Development        Game Development FAQs Programming Languages - More    ASP Programming        ASP Programming FAQs    .Net Development        .Net Development FAQs    Visual Basic Programming        Visual Basic Programming FAQs    Software Design        Software Design FAQs    ColdFusion Development        ColdFusion Development FAQs    Delphi Programming        Delphi Programming FAQs    Regex Programming        Regex Programming FAQs    XML Programming        XML Programming FAQs    Other Programming Languages        Other Programming Languages FAQs Web Design    HTML Programming        HTML Programming FAQs    JavaScript Development        JavaScript Development FAQs    CSS Help        CSS Help FAQs    Flash Help        Flash Help FAQs    Photoshop Help        Photoshop Help FAQs    Web Design Help        Web Design Help FAQs    Website Critiques        Website Critiques FAQs    Search Engine Optimization        Search Engine Optimization FAQs Mobile Programming    Mobile Programming        Mobile Programming FAQs    iPhone SDK Development        iPhone SDK Development FAQs    Android Development        Android Development FAQs    BlackBerry Development        BlackBerry Development FAQs Web Site Management    Business Help        Business Help FAQs    Development Software        Development Software FAQs    Scripts        Scripts FAQs Databases    Database Management        Database Management FAQs    DB2 Development        DB2 Development FAQs    MySQL Help        MySQL Help FAQs    PostgreSQL Help        PostgreSQL Help FAQs    Firebird SQL Development        Firebird SQL Development FAQs    MS SQL Development        MS SQL Development FAQs    Oracle Development        Oracle Development FAQs    LDAP Programming        LDAP Programming FAQs System Administration    Mail Server Help        Mail Server Help FAQs    Apache Development        Apache Development FAQs    Security and Cryptography        Security and Cryptography FAQs    Antivirus Protection        Antivirus Protection FAQs    DNS        DNS FAQs    IIS        IIS FAQs    Networking Help        Networking Help FAQs    FTP Help        FTP Help FAQs Operating Systems    BSD Help        BSD Help FAQs    Linux Help        Linux Help FAQs    UNIX Help        UNIX Help FAQs    Windows Help        Windows Help FAQs    Mac Help        Mac Help FAQs Web Hosting    Web Hosting        Web Hosting FAQs    Free Web Hosting        Free Web Hosting FAQs    Web Hosting Requests        Web Hosting Requests FAQs    Web Hosting Offers        Web Hosting Offers FAQs Computer Hardware    Computer Hardware    CPUs        CPUs FAQs    Cooling        Cooling FAQs    Embedded Programming        Embedded Programming FAQs    Motherboards        Motherboards FAQs    Multimedia Hardware        Multimedia Hardware FAQs Other    Dev Shed Lounge        Dev Shed Lounge FAQs    Development Articles        Development Articles FAQs    Beginner Programming        Beginner Programming FAQs    Hire A Programmer        Hire A Programmer FAQs    Project Help Wanted        Project Help Wanted FAQs Latest News Updated Hourly    Technology News    Business News    Science News Forum Information    Forum Rules/Guidelines        Forum Rules/Guidelines FAQs    Forum Announcements        Forum Announcements FAQs    Dev Shed Gaming Center        Go to the Dev Shed Battle Arena        Go to the Dev Shed Arcade Games        Go to the Legend of the Green Dragon    Suggestions & Feedback        Suggestions & Feedback FAQs

 Forums: » Register « |  Free Tools |  User CP |  Games |  Calendar |  Members |  FAQs |  Sitemap |  Support |