Sorting algorithms/Selection sort: Difference between revisions
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select_r first [] lst</lang> |
select_r first [] lst</lang> |
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=={{header|Python}}== |
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<lang python> |
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def selectionSort(list): |
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for i in range(0,len(list)-1): |
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min = i |
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for j in range(i+1,len(list)): |
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if list[j] < list[min]: |
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min = j |
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list[i],list[min] = list[min],list[i] |
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return list |
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</lang> |
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=={{header|Standard ML}}== |
=={{header|Standard ML}}== |
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Revision as of 21:51, 12 May 2009
You are encouraged to solve this task according to the task description, using any language you may know.
Sorting Algorithm
This is a sorting algorithm. It may be applied to a set of data in order to sort it.
For comparing various sorts, see compare sorts.
For other sorting algorithms, see sorting algorithms, or:
Heap sort | Merge sort | Patience sort | Quick sort
O(n log2n) sorts
Shell Sort
O(n2) sorts
Bubble sort |
Cocktail sort |
Cocktail sort with shifting bounds |
Comb sort |
Cycle sort |
Gnome sort |
Insertion sort |
Selection sort |
Strand sort
other sorts
Bead sort |
Bogo sort |
Common sorted list |
Composite structures sort |
Custom comparator sort |
Counting sort |
Disjoint sublist sort |
External sort |
Jort sort |
Lexicographical sort |
Natural sorting |
Order by pair comparisons |
Order disjoint list items |
Order two numerical lists |
Object identifier (OID) sort |
Pancake sort |
Quickselect |
Permutation sort |
Radix sort |
Ranking methods |
Remove duplicate elements |
Sleep sort |
Stooge sort |
[Sort letters of a string] |
Three variable sort |
Topological sort |
Tree sort
In this task, the goal is to sort an array (or list) of elements using the Selection sort algorithm. It works as follows:
First find the smallest element in the array and exchange it with the element in the first position, then find the second smallest element and exchange it with the element in the second position, and continue in this way until the entire array is sorted. Its asymptotic complexity is O(n2) making it inefficient on large arrays.
Ada
<lang ada> with Ada.Text_IO; use Ada.Text_IO;
procedure Test_Selection_Sort is
type Integer_Array is array (Positive range <>) of Integer;
procedure Sort (A : in out Integer_Array) is
Min : Positive;
Temp : Integer;
begin
for I in A'First..A'Last - 1 loop
Min := I;
for J in I + 1..A'Last loop
if A (Min) > A (J) then
Min := J;
end if;
end loop;
if Min /= I then
Temp := A (I);
A (I) := A (Min);
A (Min) := Temp;
end if;
end loop;
end Sort;
A : Integer_Array := (4, 9, 3, -2, 0, 7, -5, 1, 6, 8);
begin
Sort (A);
for I in A'Range loop
Put (Integer'Image (A (I)) & " ");
end loop;
end Test_Selection_Sort; </lang> Sample output:
-5 -2 0 1 3 4 6 7 8 9
ALGOL 68
<lang algol> MODE DATA = REF CHAR;
PROC in place selection sort = (REF[]DATA a)VOID: BEGIN
INT min;
DATA temp;
FOR i FROM LWB a TO UPB a DO
min := i;
FOR j FROM i + 1 TO UPB a DO
IF a [min] > a [j] THEN
min := j
FI
OD;
IF min /= i THEN
temp := a [i];
a [i] := a [min];
a [min] := temp
FI
OD
END # in place selection sort #;
[32]CHAR data := "big fjords vex quick waltz nymph"; [UPB data]DATA ref data; FOR i TO UPB data DO ref data[i] := data[i] OD; in place selection sort(ref data); FOR i TO UPB ref data DO print(ref data[i]) OD; print(new line); print((data)) </lang> Output:
abcdefghiijklmnopqrstuvwxyz big fjords vex quick waltz nymph
AWK
<lang awk>function getminindex(gl, gi, gs) {
min = gl[gi]
gm = gi
for(gj=gi; gj <= gs; gj++) {
if ( gl[gj] < min ) {
min = gl[gj]
gm = gj
}
}
return gm
}
{
line[NR] = $0
} END { # sort it with selection sort
for(i=1; i <= NR; i++) {
mi = getminindex(line, i, NR)
t = line[i]
line[i] = line[mi];
line[mi] = t
}
#print it
for(i=1; i <= NR; i++) {
print line[i]
}
}</lang>
C
<lang c>#include <stdio.h>
int getminindex(int *a, int s, int b)
{
int i, min=a[s], mi=s;
for(i=s; i < b; i++)
{
if ( a[i] < min ) { min = a[i]; mi = i; }
}
return mi;
}
void selectionsort(int *a, int s) {
int i, t, mi;
for(i=0; i<s ; i++)
{
mi = getminindex(a, i, s);
t = a[i]; a[i] = a[mi]; a[mi] = t;
}
}
int main()
{
int ar[] = { 5, 200, 1, 65, 30, 99, 2, 0 };
int i;
selectionsort(ar, 8);
for(i=0; i<8; i++)
{
printf("%d\n", ar[i]);
}
return 0;
} </lang>
Sample output
0 1 2 5 30 65 99 200
D
<lang d> // Written in D 2.0.
import std.stdio;
void swap(T)(ref T lhs, ref T rhs) {
T temp = lhs; lhs = rhs; rhs = temp;
}
void selectionSort(T)(T[] data) {
foreach(i; 0..data.length) {
size_t minIndex = i;
foreach(j; i + 1..data.length) {
if(data[j] < data[minIndex]) {
minIndex = j;
}
}
swap(data[i], data[minIndex]);
}
}
void main() {
auto foo = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 8, 9, 7, 9, 3, 2]; selectionSort(foo); writeln(foo);
} </lang>
Forth
<lang forth> defer less? ' < is less?
- least ( start end -- least )
over cell+ do i @ over @ less? if drop i then cell +loop ;
- selection ( array len -- )
cells over + tuck ( end start end ) cell- swap do ( end ) i over least ( end least ) i @ over @ i ! swap ! cell +loop drop ;
create array 8 , 1 , 4 , 2 , 10 , 3 , 7 , 9 , 6 , 5 ,
array 10 selection array 10 cells dump </lang>
Fortran
<lang fortran> PROGRAM SELECTION
IMPLICIT NONE
INTEGER :: intArray(10) = (/ 4, 9, 3, -2, 0, 7, -5, 1, 6, 8 /) WRITE(*,"(A,10I5)") "Unsorted array:", intArray CALL Selection_sort(intArray) WRITE(*,"(A,10I5)") "Sorted array :", intArray
CONTAINS
SUBROUTINE Selection_sort(a) INTEGER, INTENT(IN OUT) :: a(:) INTEGER :: i, minIndex, temp
DO i = 1, SIZE(a)-1
minIndex = MINLOC(a(i:), 1) + i - 1
IF (a(i) > a(minIndex)) THEN
temp = a(i)
a(i) = a(minIndex)
a(minIndex) = temp
END IF
END DO
END SUBROUTINE Selection_sort
END PROGRAM SELECTION </lang> Output:
Unsorted array: 4 9 3 -2 0 7 -5 1 6 8 Sorted array : -5 -2 0 1 3 4 6 7 8 9
Haskell
<lang haskell>selectionSort [] = [] selectionSort (first:lst) = selectR first [] lst where
selectR small output [] = small : selectionSort output
selectR small output (x:xs) | x < small = selectR x (small:output) xs
| otherwise = selectR small (x:output) xs</lang>
Java
This algorithm sorts in place. The call sort(array) will rearrange the array and not create a new one. <lang java>public static void sort(int[] nums){ for(int currentPlace = 0;currentPlace<nums.length-1;currentPlace++){ int smallest = Integer.MAX_VALUE; int smallestAt = currentPlace+1; for(int check = currentPlace+1; check<nums.length;check++){ if(nums[check]<smallest){ smallestAt = check; smallest = nums[check]; } } int temp = nums[currentPlace]; nums[currentPlace] = nums[smallestAt]; nums[smallestAt] = temp; } } </lang>
MAXScript
fn selectionSort arr =
(
local min = undefined
for i in 1 to arr.count do
(
min = i
for j in i+1 to arr.count do
(
if arr[j] < arr[min] then
(
min = j
)
)
swap arr[i] arr[min]
)
arr
)
data = selectionSort #(4, 9, 3, -2, 0, 7, -5, 1, 6, 8)
print data
OCaml
<lang ocaml>let rec selection_sort = function
[] -> []
| first::lst ->
let rec select_r small output = function
[] -> small :: selection_sort output
| x::xs when x < small -> select_r x (small::output) xs
| x::xs -> select_r small (x::output) xs
in
select_r first [] lst</lang>
Python
<lang python> def selectionSort(list):
for i in range(0,len(list)-1):
min = i
for j in range(i+1,len(list)):
if list[j] < list[min]:
min = j
list[i],list[min] = list[min],list[i]
return list
</lang>
Standard ML
<lang sml>fun selection_sort [] = []
| selection_sort (first::lst) =
let
fun select_r small ([], output) = small :: selection_sort output
| select_r small (x::xs, output) =
if x < small then
select_r x (xs, small::output)
else
select_r small (xs, x::output)
in
select_r first (lst, [])
end</lang>
Tcl
uses package struct::list from tcllib
<lang tcl>package require Tcl 8.5
package require struct::list
proc selectionsort {A} {
set len [llength $A]
for {set i 0} {$i < $len - 1} {incr i} {
set min_idx [expr {$i + 1}]
for {set j $min_idx} {$j < $len} {incr j} {
if {[lindex $A $j] < [lindex $A $min_idx]} {
set min_idx $j
}
}
if {[lindex $A $i] > [lindex $A $min_idx]} {
struct::list swap A $i $min_idx
}
}
return $A
}
puts [selectionsort {8 6 4 2 1 3 5 7 9}] ;# => 1 2 3 4 5 6 7 8 9</lang>