selectionsort with java

7/28/2019 SelectionSort With Java

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The Selection Sort

Mr. Dave ClausenMr. Dave Clausen

La Caada High SchoolLa Caada High School


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The Selection SortDescription

The Selection Sort searches (linear search) all of The Selection Sort searches (linear search) all of the elements in a list until it finds the smallestthe elements in a list until it finds the smallest

element. It swaps this with the first element inelement. It swaps this with the first element inthe list. Next it finds the smallest of the remainingthe list. Next it finds the smallest of the remainingelements, and swaps it with the second element.elements, and swaps it with the second element.

Repeat this process until you compare only the lastRepeat this process until you compare only the lasttwo elements in the list.two elements in the list.


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The Selection SortAlgorithm

For each index positionFor each index position i

Find the smallest data value in the arrayFind the smallest data value in the arrayfrom positionsfrom positions i through lengththrough length -- 1, where1, wherelength is the number of data valueslength is the number of data values

stored.stored. Exchange (swap) the smallest value withExchange (swap) the smallest value with

the value at positionthe value at positioni..


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We start by searching for thesmallest element in the List.

A Selection Sort Example

Smallest ?


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Smallest ?


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Smallest !


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Swap


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Swapped


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After the smallest elementis in the first position, wecontinue searching withthe second element and look for the next smallestelement.

Smallest ?


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In this special case, thenext smallest element is inthe second positionalready. Swapping keepsit in this position.

Smallest !


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Swapping keeps it in this position.

Swapped


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After the next smallest element isin the second position, we continue

searching with the third elementand look for the next smallestelement.

Smallest ?


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Smallest !


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Swap


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Swapped


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Smallest ?


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Smallest ?


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Smallest !


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Swap


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Swapped


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The last two elements are inorder, so no swap is necessary.


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What Swapping Means6

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TEMP

Place the first element intothe Temporary Variable.

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TEMP

Replace the first elementwith the value of the

smallest element.

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TEMP

Replace the third element(in this example) with the

Temporary Variable.

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Java Source Code: Selection Sort public static void selectionSort(int[] list){

for (int index = 0; index < list.length - 1; index ++){

int minIndex = findMinimum(list, index );if (minIndex != index )swap(list, index , minIndex);

}}


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Java Code For Find Minimum

p public static int findMinimum(int[] list, int first){

int minIndex = first;

for (int index = first + 1; index < list.length; index ++)if (list[index] < list[minIndex])

minIndex = index ;

return minIndex;}


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Java Code for Swap Procedure public static void swap(int[] list, int x, int y){

int temp = list[x];

list[x] = list[y];list[y] = temp;

}


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C ++ Code For Selection Sortvoid Selection_Sort (void Selection_Sort ( apvector apvector & v) & v){{

int min_index = 0;int min_index = 0;

for (int index = 0; index < vfor (int index = 0; index < v .. length( )length( ) -- 1; ++index)1; ++index){{

min_index = Find_Minimum (v, index);min_index = Find_Minimum (v, index);

if (min_index ! = index)if (min_index ! = index)

Swap_Data ( v [index], v [min_index])Swap_Data ( v [index], v [min_index])

}}

}}

// Selection_Sort// Selection_Sort


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C ++ Code For Find Minimum

int Find_Minimum (constint Find_Minimum (const apvector apvector & v, int first) & v, int first)

{{

int min_index = first;int min_index = first;for (int index = first + 1; index < vfor (int index = first + 1; index < v .. length( ); ++index)length( ); ++index)

if ( v[index] < v[min_index])if ( v[index] < v[min_index])

min_index = index;min_index = index;

return min_index;return min_index;

}}// Find_Minimum// Find_Minimum


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C ++ Code for Swap Procedure

void Swap_Data (int &number1, int &number2)void Swap_Data (int &number1, int &number2)

{{

int temp;int temp;

temp = number1;temp = number1;number1 = number2;number1 = number2;

number2 = temp;number2 = temp;

}}// End of Swap_Data function// End of Swap_Data function


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Pascal Code For Selection Sort procedure procedure SelectionSortSelectionSort ((var IntArrayvar IntArray :: IntNumbersIntNumbers ););

var var element,element, SmallIndexSmallIndex , index: integer;, index: integer;

begin begin

for element := 1 to (for element := 1 to ( MaxNumMaxNum -- 1) do1) do begin begin

SmallIndexSmallIndex := element;:= element;

for index := (element + 1) tofor index := (element + 1) to MaxNumMaxNum dodo

if if IntArrayIntArray [index]


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Pascal Code for Swap Procedure procedure Swap ( procedure Swap ( var var number1, number2: integer);number1, number2: integer);

var var

temp: integer;temp: integer;

begin begintemp := number1;temp := number1;

number1 := number2;number1 := number2;

number2 := tempnumber2 := tempend; {Swap}end; {Swap}


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BASIC Code For Selection Sort8000 REM #################8000 REM #################8010 REM Selection Sort8010 REM Selection Sort

8020 REM #################8020 REM #################

8030 FOR ELEMENT = 1 TO MAXNUM8030 FOR ELEMENT = 1 TO MAXNUM -- 118040 ::8040 :: SmallIndexSmallIndex = element= element

8050 ::FOR INDEX = (element + 1) TO MAXNUM8050 ::FOR INDEX = (element + 1) TO MAXNUM

8060 ::::::IF N (INDEX) < N (8060 ::::::IF N (INDEX) < N ( SmallIndexSmallIndex ) THEN) THEN SmallIndexSmallIndex = INDEX= INDEX

8070 ::NEXT INDEX8070 ::NEXT INDEX

8080 ::TEMP = N (element)8080 ::TEMP = N (element)

8090 ::N (element) = N (8090 ::N (element) = N ( SmallIndexSmallIndex ))

8100 ::N (8100 ::N ( SmallIndexSmallIndex ) = TEMP) = TEMP8110 NEXT ELEMENT8110 NEXT ELEMENT

8120 RETURN8120 RETURN


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Big - O Notation

BigBig

--

O notation is used to describe the efficiencyO notation is used to describe the efficiency

of a search or sort. The actual time necessary toof a search or sort. The actual time necessary tocomplete the sort varies according to the speed of complete the sort varies according to the speed of

your system.your system. BigBig -- O notation is an approximateO notation is an approximatemathematical formula to determine how manymathematical formula to determine how manyoperations are necessary to perform the search or operations are necessary to perform the search or

sort. The Bigsort. The Big -- O notation for the Selection Sort isO notation for the Selection Sort isO(nO(n 22), because it takes approximately n), because it takes approximately n 22 passes to passes tosort the elements.sort the elements.

selectionsort with java

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