Sorting Arrays

1
Sorting Arrays

• ANSI-C

2
Selection Sort

• Assume want to sort a table of integers, of size
  length, in increasing order.
• Sketch of algorithm
• Find position of smallest in table0..length-1,
  place it in place 0
• Find position of smallest in table 1..length-1,
  place it in place 1
• Find position of smallest in table
  2..length-1,, place it in place 2
• .
• Find position of smallest in table
  length-2..length-1, place it in place length-2
• Find position of smallest in table
  length-1..length-1, place it in place length 1
  
• General form
• Find position of smallest in tablei..length-1
  and place it in place i
• For i0..length-2
• It calls for a loop

3

• int i 0
• while (i lt ?)
• find position of smallest in tablei..length-1
  
• place element at that position in place i
• i i 1
• So, we need to write two functions
• int smallestPos ( int table, int first, int
  last)
• And a function that interchanges the elements in
  the array in places i, that the position where
  the smallest in tablei..length-1
• void interchange( int table, int i, int k)

4

• void selectionSort( int table, int length)
• int i 0
• int smallest
• while (i lt length - 1)
• smallest smallestPos(table, i, length-1)
• interchange( table, i, smallest)
• i i 1

5

• int smallestPos ( int table, int first, int
  last)
• int pos first
• int i first 1
• while ( i lt last)
• if (tablepos gt tablei)
• pos i
• i i 1
• return pos

6

• void interchange( int table, int i, int k)
• int temp tablei
• tablei tablek
• tablek temp