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

[learner999]

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.

[jonnin]

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.

[George PlusPlus]

What exactly are a, d, x and w in your tuples? Previously defined variables?

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

#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.

[George PlusPlus]

#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

[learner999]

Thank you so much @jonnin and @George P

[seeplus]

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)?