How to manipulate arrays?
6 visualizzazioni (ultimi 30 giorni)
Mostra commenti meno recenti
Shawn Simon
il 31 Ott 2015
Commentato: Star Strider
il 1 Nov 2015
Hello! I am trying to create a script in which I sort an array in descending order without using any sort function. So far, I came up with this:
A = [2 1 4 3 6 5 8 7 10 9 12 11 14 13 16 15 18 17 20 19];
n = 1;
while n <= length(A)
if A(n) < A(n+1)
tmp = A(n);
A(n) = A(n+1);
A(n+1) = tmp;
end
n = n +1;
end
I thought it would be this simple, but it apparently isn't. One of the things I do not know how to do is place a value of one array into a new array, which I feel is vital in a script like this, but I did not know how to do it, so I did not implement it. Any help will be appreciated. Thank you in advance!
0 Commenti
Risposta accettata
Star Strider
il 31 Ott 2015
Assigning one array to another is like assigning any other variable. Consider the B = A assignment here.
It looks as though you want to do a bubble sort, the simplest sorting algorithm. You’re close. This is how I would do it:
A = [2 1 4 3 6 5 8 7 10 9 12 11 14 13 16 15 18 17 20 19];
B = A; % Original Vector
swap = true;
while swap
swap = false;
for n = 1:length(A)-1
if A(n) < A(n+1)
tmp = A(n);
A(n) = A(n+1);
A(n+1) = tmp;
swap = true;
end
end
end
The idea is to iterate the swapping loop until the ‘swap’ test is false ( i.e. no swap was made during a particular iteration of the vector ). Your loop sorts in descending order. You can add a counter to keep track of the number of swaps that were made.
5 Commenti
Più risposte (2)
Walter Roberson
il 31 Ott 2015
B(m) = A(n);
for some m and n.
However, that is not the reason your code is not working. You have implemented one pass of a "bubble sort". If your input were [3 2 1] then when n=1 it would change to [2 3 1] and then when n=2 it would change to [2 1 3] (and in the next pass it would crash because you would be trying to compare A(3) to the non-existent A(4), but that is trivially fixed.) Notice that the "2" and the "1" never get compared to each other. You will need to re-examine your strategy to fix that.
timo
il 31 Ott 2015
Dont reinvent the wheel
>> x =py.list([5,4,1,2,3,7])
x =
Python list with no properties.
[5.0, 4.0, 1.0, 2.0, 3.0, 7.0]
>> x.sort
>> x
x =
Python list with no properties.
[1.0, 2.0, 3.0, 4.0, 5.0, 7.0]
3 Commenti
Star Strider
il 1 Nov 2015
It could be just to see how a sort script works, and to learn programming processes and logic in the process. Some people have the sort of insatiable curiosity about such things that will carry them far. Shawn is likely one such person.
Vedere anche
Categorie
Scopri di più su Loops and Conditional Statements in Help Center e File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!