04. Selection Sort

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(C) GOYANI MAHESH(C) GOYANI MAHESH 11

DATASTRUCTURES

MAHESH GOYANI

MAHATMAGANDHI INSTITUE OF TECHNICALEDUCATION & RESEARCH CENTER

[email protected]


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SELECTIONSORT


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In plain English: Find the smallest element and place itin thefirst position, swapping places with the original first element;continue with successive elements

In pseudo code:

for each element from first to last

find smallest successive element

swap the elements

TERMINOLOGY


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5 8 20 10 7

5 7 20 10 8

5 7 8 10 20

20 8 5 10 7

5 7 8 10 20

Swapping Action


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Start by finding the smallest entry.

Swap the smallest entry with the first entry.

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Part of the array is now sorted.

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Sorted side Unsorted side

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Find the smallest elementin the unsorted side.


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Find the smallest elementin the unsorted side.

Swap with the front of the unsorted side.


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We have increased the size of the sorted side by oneelement.


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The processThe processcontinues...!!continues...!!


Smallest

from

unsorted

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Sorted side Unsorted sideSorted side

is bigger

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SORTED..!!


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22 45 13 97 432213

45 97 432213 4522

22 45 974313

97 4313 4522 4543

22 97 454313 45 97

DONE..!!

Simulation


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1212 88881212121288

661212666612121212 17172222 881414

66 17172222 1414

Simulation


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14141414 17172222 171722222222171788

22221212 1212222288 1212222266 17171414

66 1212

Simulation


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7 2 8 5 4

2 7 8 5 4

2 4 8 5 7

2 4 5 8 7

2 4 5 7 8

Simulation


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Analysis of the code shows that the outer loop executes n-1 times;

for the firstiteration of the outer loop, the inner loop executes n-1times

for the seconditeration of the outer loop, the inner loop executesn-2 times

etc

for the lastiteration of the outer loop, the inner loop executes 1time

thus the execution time is (n-1) + (n-2) + (n-3) + + 3 + 2 +

1

the sum of this series is (n2 - n) / 2

selection sortis O(n2 )

COMPLEXITY

04. Selection Sort

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