Most efficient way to find the greatest of three ints

Question

Below is my pseudo code.

function highest(i, j, k)
{
  if(i > j && i > k)
  {
    return i;
  }
  else         


        

Answer 1

To find the greatest you need to look at exactly 3 ints, no more no less. You're looking at 6 with 3 compares. You should be able to do it in 3 and 2 compares.

int ret = max(i,j);
ret = max(ret, k);
return ret;

Answer 2

For a question like this, there is no substitute for knowing just what your optimizing compiler is doing and just what's available on the hardware. If the fundamental tool you have is binary comparison or binary max, two comparisons or max's are both necessary and sufficient.

I prefer Ignacio's solution:

result = i;
if (j > result)
  result = j;
if (k > result)
  result = k;
return result;

because on the common modern Intel hardware, the compiler will find it extremely easy to emit just two comparisons and two cmov instructions, which place a smaller load on the I-cache and less stress on the branch predictor than conditional branches. (Also, the code is clear and easy to read.) If you are using x86-64, the compiler will even keep everything in registers.

Note you are going to be hard pressed to embed this code into a program where your choice makes a difference...

Answer 3

I think by "most efficient" you are talking about performance, trying not to waste computing resources. But you could be referring to writing fewer lines of code or maybe about the readability of your source code. I am providing an example below, and you can evaluate if you find something useful or if you prefer another version from the answers you received.

/* Java version, whose syntax is very similar to C++. Call this program "LargestOfThreeNumbers.java" */
class LargestOfThreeNumbers{
    public static void main(String args[]){
        int x, y, z, largest;
        x = 1;
        y = 2;
        z = 3;
        largest = x;
        if(y > x){
            largest = y;
            if(z > y){
                largest = z;
            }
        }else if(z > x){
            largest = z;
        }
        System.out.println("The largest number is: " + largest);
    }
}

Answer 4

There is a proposal to include this into the C++ library under N2485. The proposal is simple, so I've included the meaningful code below. Obviously, this assumes variadic templates

template < typename T >
const T & max ( const T & a )
{ return a ; }

template < typename T , typename ... Args >
const T & max( const T & a , const T & b , const Args &... args )
{ return  max ( b > a ? b : a , args ...); }

Answer 5

In C# finding the greatest and smallest number between 3 digit

static void recorrectFindSmallestNumber()
{
int x = 30, y = 22, z = 11;
if (x < y)
{
if (x < z)
{
Console.WriteLine("X is Smaller Numebr {0}.", x);
}
else
{
Console.WriteLine("z is Smaller Numebr {0}.", z);
}
}
else if (x > y)
{
if (y < z)
{
Console.WriteLine("y is Smaller number.{0}", y);
}
else
{
Console.WriteLine("z is Smaller number.{0}", z);
}
}
 else
{

}
}

=================================================================

static void recorrectFindLargeNumber()
{
int x, y, z;
Console.WriteLine("Enter the first number:");
x = int.Parse(Console.ReadLine());
Console.WriteLine("Enter the second number:");
y = int.Parse(Console.ReadLine());
Console.WriteLine("Enter the third nuumnber:");
z = int.Parse(Console.ReadLine());
if (x > y)
{
if (x > z)
{
Console.WriteLine("X is Greater numbaer: {0}.", x);
}
else
{
Console.WriteLine("Z is greatest number: {0}.", z);
}
}
else if (x < y)
{
if (y > z)
{
Console.WriteLine("y is Greater Number: {0}", y);
}
else 
{
Console.WriteLine("Z is Greater Number; {0}", z);                
}
}
else
{
                
}
}

Answer 6

public int maximum(int a,int b,int c){
    int max = a;
    if(b>max)
        max = b;
    if(c>max)
        max = c;
    return max;
}