how do I add function to find the two highest numbers from user input in this code?

[teooo5]

how do I add function to find the two highest numbers from user input in this code? I will need then to add subtract, multiply and divide the two highest numbers.

#include <iostream>

void sortNum(int& num1, int& num2, int& num3);

int main()
{
int firstNum, secondNum, thirdNum;
std::cout << "Enter first number: ";
std::cin >> firstNum;
std::cout << "Enter second number: ";
std::cin >> secondNum;
std::cout << "Enter third number: ";
std::cin >> thirdNum;
std::cout << "Numbers not in order: " << firstNum << ' ' << secondNum << ' ' << thirdNum << '\n';


sortNum(firstNum, secondNum, thirdNum);


std::cout << "Numbers in order: " << firstNum << ' ' << secondNum << ' ' << thirdNum << '\n';
}

void sortNum(int& num1, int& num2, int& num3)
{

if(num1 > num2)
{
int temp = num1;
num1 = num2;
num2 = temp;
}
if (num2 > num3)
{
int temp = num2;
num2 = num3;
num3 = temp;
}
}

[Shadowwolf]

A function to sort three integers in order could be:

void sortNum(int& num1, int& num2, int& num3)
{
    int max = std::max(std::max(num1,num2),num3); //The maximum value
    int min = std::min(std::min(num1,num2),num3); //The minimum value
    int medium;
    if(num1 != max && num1 != min) //The other value
        medium = num1;
    else if(num2 != max && num2 != min)
        medium = num2;
    else
        medium = num3;
    //And store the results
    num1 = max;
    num2 = medium;
    num3 = min;
}

This isn't an efficient implementation, but it should work.

[danjiun]

From you code , i interfiere you want to have a minimum element at num1 (not at num3)
You can also do it like this :

void sortNum(int& num1, int& num2, int& num3)
{
    auto swap = [] (int& numA, int& numB) { int temp=numA; numA=numB;numB=temp;};
    if (num1>num2) {
        if (num1>num3) {
            if(num2>num3) swap(num1,num3);
            else { swap(num1,num2); swap(num2,num3);}
        }
        else swap(num1,num2);
    } 
    else {
        if (num2>num3) {
            if (num1<num3) swap(num2,num3);
            else { swap(num1,num3); swap(num2,num3);}
        }
}

I think, using lambda function in C++11 would be same fast, it would insert inline.
But, if you not want to use it, then simply substitue each swap by
int temp=numA; numA=numB;numB=temp;
I believe you search a quick algorithm,
This code would give you less swaps.
greatings, Daniel

[coder777]

You may use the std::swap:

http://www.cplusplus.com/reference/utility/swap/?kw=swap

[danjiun]

Yes ! This would be better, because i am sure that g++ will be optimized for integer swap.
It is possible that a integer swap between 2 directions can be done in one ensambler instruction ?
greatings, Daniel

[cire]

You can also do it like this :

That is some complicated code for a swapping algorithm.

void sortNum(int& num1, int& num2, int& num3)
{
    using std::swap;

    if (num1 > num2)
        swap(num1, num2);

    if (num2 > num3)
        swap(num2, num3);

    if (num1 > num2)
        swap(num1, num2);
}

[danjiun]

Solution of "cire" i believe is the most good looking and easier. However always use 3 swaps.
Solution which i (danjiun) give, it do in 0,1 or 2 swaps, but is not so good looking.
I have another idea :
If we know limits about this numbers, for example, have a minimum and a maximum value, and this range is not too big, and we want to use many many times this function, you can also "precalculate" results, and assign quicker.
Daniel

[cire]

Solution of "cire" i believe is the most good looking and easier. However always use 3 swaps.

Of the six possible relative orders, our code differs in the number of swaps on only 1 relative order.

[danjiun]

You are right. Only in one case can happen. Sorry.

[teooo5]

sorry guys, I'm at the very beginning with c++! I don't seem to understand how to add the output sum, difference, product and division of the two highest input numbers. any help?

[danjiun]

You can do like this :

#include <iostream>

void sortNum(int& num1, int& num2, int& num3);

int main()
{
int firstNum, secondNum, thirdNum;
std::cout << "Enter first number: ";
std::cin >> firstNum;
std::cout << "Enter second number: ";
std::cin >> secondNum;
std::cout << "Enter third number: ";
std::cin >> thirdNum;
std::cout << "Numbers not in order: " << firstNum << ' ' << secondNum << ' ' << thirdNum << '\n';
sortNum(firstNum, secondNum, thirdNum);
std::cout << "Numbers in order: " << firstNum << ' ' << secondNum << ' ' << thirdNum << '\n';
std::cout << "Sum of highest numbers : " << secondNum+thirdSum << '\n';
std::cout << "Difference of highest numbers : " << thirdSum-secondNum << '\n';
std::cout << "Product of highest numbers : " << secondNum*thirdSum << '\n';
std::cout << "Division of highest numbers : " << double(thirdSum)/secondNum << '\n';
}

void sortNum(int& num1, int& num2, int& num3)
{

using std::swap;

    if (num1 > num2)
        swap(num1, num2);

    if (num2 > num3)
        swap(num2, num3);

    if (num1 > num2)
        swap(num1, num2);
}
}

Daniel