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Finding minimum element of a tuple on the basis of first element

Jun 21, 2024 at 9:15pm UTC
learner999 (102)
Hello everyone,

I do not know, if it is possible to find the minimum first element in a tuple without using sort function. I have a tuple like this : data=[ ( 23, a, 3.78, d), ( 11, x, 5.8, w)] . I need to obtain the second element which is (11, x, 5.8, w) since 11<23. Is there any way to do it without using sort function ?

Thank you so much in advance.

Jun 22, 2024 at 12:50am UTC
jonnin (11378)
of course it is. you can iterate all your tuples and keep track of the smallest one via your condition. You don't WANT to sort data to find the lowest element:
iterating each element once and finding the smallest takes N operations.
Sorting, usually, takes at least N(lg(N)) operations, which is only a little more than N for a few items but quite a lot more when you start having many items.


if you only have 2 items, its just a flat compare.
Last edited on Jun 22, 2024 at 12:51am UTC
Jun 22, 2024 at 7:29pm UTC
George PlusPlus (5634)
What exactly are a, d, x and w in your tuples? Previously defined variables?

There 3 different ways to access a tuple's elements.

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#include <iostream>
#include <tuple>

int main( )
{
   auto tup = std::make_tuple( 11, 'x', 5.8, 'w' );

   // get specific element within a tuple (zero-based)
   std::cout << get<1>( tup ) << '\n';

   // tie tuple values to variables, std::ignore used to discard elements
   char ch;
   std::tie( std::ignore, ch, std::ignore, std::ignore ) = tup;

   std::cout << ch << '\n';

   // C++17 structured binding
   auto [ a, b, c, d ] = tup;

   std::cout << b << '\t' << c << '\n';

   // if x and w are other variables....
   int    x { 42 };
   double w { 8.65 };

   auto tup2 = std::make_tuple( 11, x, 5.8, w );

   std::cout << get<1>( tup2 ) << '\n';
}

http://coliru.stacked-crooked.com/a/08c29256b288faf4

Personally I prefer either direct access to a tuple's element using get or structured binding. I especially like structured binding since using auto means I don't have to know what the types are contained inside the tuple.

Which method I use depends on the circumstances.
Jun 22, 2024 at 7:39pm UTC
George PlusPlus (5634)
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#include <iostream>
#include <tuple> // https://en.cppreference.com/w/cpp/utility/tuple
#include <vector>

int main( )
{
   std::vector data { std::make_tuple( 23, 'a', 3.78, 'd' ),
                      std::make_tuple( 11, 'x', 5.8, 'w' ) };

   auto [a, b, c, d] = data[0];

   std::cout << c << '\n';
}

http://coliru.stacked-crooked.com/a/9707b1ddc659e291
Jun 23, 2024 at 8:38am UTC
learner999 (102)
Thank you so much @jonnin and @George P
Jun 23, 2024 at 9:11am UTC
seeplus (6517)
I have a tuple like this : data=[ ( 23, a, 3.78, d), ( 11, x, 5.8, w)]


Is data a tuple of 2 elements each being a tuple of 4 elements (ie a tuple of tuples)?
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