Determine the largest number among three numbers using C++

Question

How can I determine the largest number among three numbers using C++?

I need to simplify this

 w=(z>((x>y)?x:y)?z:((x>y)?x:y));

Conditionals do not simplify this.

Define "simplify". If it's a code golf problem you should post it here: https://codegolf.stackexchange.com/ — XCS, Nov 21 '17 at 13:37
Possible duplicate of [Find maximum of three number in C without using conditional statement and ternary operator](https://stackoverflow.com/questions/7074010/find-maximum-of-three-number-in-c-without-using-conditional-statement-and-ternar) — Neha, Nov 21 '17 at 13:44
`(x > y) ? (x > z ? x : z) : (y > z ? y : z);` is better ordering of the brackets.. There is also `std::max_element(std::begin(array), std::end(array))` which would give you the position in the array of the maximum element. — Brandon, Nov 21 '17 at 13:48

score 20 · Accepted Answer · answered Nov 21 '17 at 13:41

20

Starting from C++11, you can do

w = std::max({ x, y, z });

answered Nov 21 '17 at 13:41

oisyn

985
4
12

@Bathsheba - But (and it's a big one) yours preforms no copies. This one I'd wager copies all the elements (though I won't encourage anyone to optimize prematurely based on this). – StoryTeller - Unslander Monica Nov 21 '17 at 13:48
1

@StoryTeller: Careful: I've already upvoted 2 answers of yours today. – Bathsheba Nov 21 '17 at 13:48
I guess! Stackoverflow is turning to trading reputation website! :D – Neha Nov 21 '17 at 13:53
@StoryTeller That argument works both ways. In the two-argument version of `std::max`, arguments are passed by references. For built-in numeric types or small POD types, passing the value is usually cheaper than passing a reference and dereferencing the references in the function itself. In practice, it will probably all be inlined. But yes, good point, this is something worth considering. – oisyn Nov 21 '17 at 13:55
2

@NehaGupta - Hardly. Bathsheba and I just happen to frequent the same tags, and engage in friendly banter. – StoryTeller - Unslander Monica Nov 21 '17 at 13:56
;-)͏͏͏͏͏͏͏͏͏͏͏͏͏ – Bathsheba Nov 21 '17 at 13:57
@oisyn - Of course, no disrespect to your answer. I can't really choose between the two myself :) – StoryTeller - Unslander Monica Nov 21 '17 at 13:57
Here is the solution I found: `w = ((y > z) || (x > z)) ? ((x > y) ? x: y) :z;`. It is utilizes less operations and very transparent. – trafalgarLaww Nov 21 '17 at 17:12
I think they should've made a C++11 style varags version of `::std::max`. – Omnifarious Nov 23 '17 at 03:43

score 8 · Answer 2 · answered Nov 21 '17 at 13:37

8

w = std::max(std::max(x, y), z);

is one way.

answered Nov 21 '17 at 13:37

Bathsheba

227,678
33
352
470

I think he's trying to use conditional operator. – Neha Nov 21 '17 at 13:40
@NehaGupta then the OP should add that to their question =) – AresCaelum Nov 21 '17 at 13:40
1

@NehaGupta: Why? – Bathsheba Nov 21 '17 at 13:40

score 2 · Answer 3 · answered Nov 21 '17 at 13:38

2

big = a > b ? (a > c ? a : c) : (b > c ? b : c) ;

answered Nov 21 '17 at 13:38

Neha

2,888
3
12
25

@YSC may i know why? – Neha Nov 21 '17 at 13:51
1

Would you trust it in a missile guidance system? – Bathsheba Nov 21 '17 at 13:52
Would you dare maintain it *if it was* in a missile guidance system? – StoryTeller - Unslander Monica Nov 21 '17 at 13:52
@Bathsheba not the best example: I'd say the world would be a better place if guidance missile engineers wrote that kind of software... – YSC Nov 21 '17 at 13:53
1

Readability goes along way. – AresCaelum Nov 21 '17 at 13:53
@YSC - In my part of the world, those missiles intercept enemy missiles. Won't be better for us if engineers wrote this kind of code. – StoryTeller - Unslander Monica Nov 21 '17 at 13:54
@YSC: Sometimes we do: http://www-users.math.umn.edu/~arnold/disasters/patriot.html – Bathsheba Nov 21 '17 at 13:54
@Bathsheba why that? – Neha Nov 21 '17 at 14:15

Siraj Alam · Answer 4 · 2017-11-21T13:40:03.283

0

Use the simple if condition

int w = x;

if(y > w)
  w = y;
if(z > w)
  w = z;

Where w is the max among three.

edited Nov 21 '17 at 13:40

answered Nov 21 '17 at 13:39

Siraj Alam

7,620
6
46
63

score 0 · Answer 5 · edited Jun 20 '20 at 09:12

0

A variant on oisyn's answer (use an initializer list) and Bathesheba's answer (invoke no copies) is to use std::ref to create an initializer list of references, and then use std::max normally:

using std::ref;
w = std::max({ref(x), ref(y), ref(z)});

This is only advantageous if creating a reference is cheaper than creating a copy (and it isn't for primitives like int)

Demo

edited Jun 20 '20 at 09:12

Community

1
1

answered Nov 21 '17 at 14:07

AndyG

38,029
8
100
134

Do we really want to leave this open to ADL? – StoryTeller - Unslander Monica Nov 21 '17 at 14:09
@StoryTeller: I thought it cleaner than passing my own lambda for comparison. – AndyG Nov 21 '17 at 14:11
I mean `ref`. We explicitly want the result of `std::ref`. If the user type defines a `ref` function the does something else entirely, this will break. – StoryTeller - Unslander Monica Nov 21 '17 at 14:12
@StoryTeller: Indeed. Probably unlikely IMO. My personal style is to always qualify the standard namespace; here I added a `using` for readability. It's certainly something every programmer needs to keep in mind when using ADL. – AndyG Nov 21 '17 at 14:18

Determine the largest number among three numbers using C++

5 Answers5

Demo

Linked

Related