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Finding the 3rd highest value

Jul 27, 2012 at 12:40pm
TheBlackCrow (4)
Can somebody teach me a code on how to find the 3rd highest value.

for example.
At start, the program ask how many loops(or numbers the user wants to add)
User inputs 10 different numbers (0,positive,negative)
Program will try to find out what is the third highest of all.
Jul 27, 2012 at 12:46pm
HiteshVaghani1 (221)
Sort the numbers..
Third number is your answer...
Jul 27, 2012 at 12:50pm
Cubbi (4774)
The function to do that in C++ is called nth_element()

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#include <vector>
#include <iostream>
#include <algorithm>
#include <functional>

int main()
{
    std::cout << "Enter 10 different numbers (0, positive, negative) ";
    std::vector<int> numbers(10);
    for(size_t n = 0; n < numbers.size(); ++n)
       std::cin >> numbers[n];

    nth_element(numbers.begin(), numbers.begin() + 2, numbers.end(),
                std::greater<int>());

    std::cout << "The 3rd largest number is " << numbers[2] << '\n';
}
Edit & run on cpp.sh


(Note: it's important that your task specifies "10 different numbers"
Jul 27, 2012 at 1:09pm
vlad from moscow (6539)
The algorithm is simple. Let assume that you have an array of n elements int a[n] fiiled with integer numbers.
In the very beginning you set 

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int max1, max2, max3;
max1 = max2 = max3 = a[o];

Then in a loop until all elements of the array will be passed you do the following comparisions


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if ( max1 < a[i] )
{
   max1 = a[i]; max2 = max1; max3 = max2;
}
else if ( max2 < a[i] )
{
   max2 = a[i]; max3 = max2;
}
else if ( max3 < a[i] )
{
   max3 = a[i];
}
Last edited on Jul 27, 2012 at 1:10pm
Jul 27, 2012 at 1:33pm
doug4 (1538)
vlad's code won't work. You need to do the assignments in the opposite order. Otherwise you are setting all of the max values to a[i];

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if ( max1 < a[i] )
{
   max3 = max2; max2 = max1; max1 = a[i];
}
else if ( max2 < a[i] )
{
   max3 = max2; max2 = a[i];
}
else if ( max3 < a[i] )
{
   max3 = a[i];
}
Jul 27, 2012 at 2:59pm
vlad from moscow (6539)
@doug4

vlad's code won't work. You need to do the assignments in the opposite order


Thanks that you pointed out my typo.
Jul 28, 2012 at 12:38am
TheBlackCrow (4)
Got it working! Thanks vlad!

My bad
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for(i=0;i<loop;i++)
     {
        cout<<"Enter a value: ";
        cin>>array[i];

        if ( max1 < array[i] )
        {
        max3 = max2; max2 = max1; max1 = array[i];
        }
        else if ( max2 < array[i] )
        {
         max3 = max2; max2 = array[i];
        }
        else if ( max3 < array[i] )
        {
        max3 = array[i];
        }  
     }

First I did this, and it does not show the correct 3rd highest but then when I use
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for(i=0;i<loop;i++)
     {
        cout<<"Enter a value: ";
        cin>>array[i];
     }
     for(i=0;i<loop;i++)
     {
        if ( max1 < array[i] )
        {
        max3 = max2; max2 = max1; max1 = array[i];
        }
        else if ( max2 < array[i] )
        {
         max3 = max2; max2 = array[i];
        }
        else if ( max3 < array[i] )
        {
        max3 = array[i];
        }  
     }

It's working fine now, thanks man.
Last edited on Jul 28, 2012 at 12:56am
Jul 28, 2012 at 12:41am
vlad from moscow (6539)
I ahve not understood you. The most highest is 6. Then 5 follows. And at last the third highest is 4.
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