mirror of https://github.com/tLDP/LDP
98 lines
3.1 KiB
Bash
98 lines
3.1 KiB
Bash
#!/bin/bash
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# bubble.sh: Bubble sort, of sorts.
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# Recall the algorithm for a bubble sort. In this particular version...
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# With each successive pass through the array to be sorted,
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#+ compare two adjacent elements, and swap them if out of order.
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# At the end of the first pass, the "heaviest" element has sunk to bottom.
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# At the end of the second pass, the next "heaviest" one has sunk next to bottom.
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# And so forth.
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# This means that each successive pass needs to traverse less of the array.
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# You will therefore notice a speeding up in the printing of the later passes.
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exchange()
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{
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# Swaps two members of the array.
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local temp=${Countries[$1]} # Temporary storage
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#+ for element getting swapped out.
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Countries[$1]=${Countries[$2]}
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Countries[$2]=$temp
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return
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}
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declare -a Countries # Declare array,
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#+ optional here since it's initialized below.
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# Is it permissable to split an array variable over multiple lines
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#+ using an escape (\)?
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# Yes.
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Countries=(Netherlands Ukraine Zaire Turkey Russia Yemen Syria \
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Brazil Argentina Nicaragua Japan Mexico Venezuela Greece England \
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Israel Peru Canada Oman Denmark Wales France Kenya \
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Xanadu Qatar Liechtenstein Hungary)
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# "Xanadu" is the mythical place where, according to Coleridge,
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#+ Kubla Khan did a pleasure dome decree.
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clear # Clear the screen to start with.
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echo "0: ${Countries[*]}" # List entire array at pass 0.
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number_of_elements=${#Countries[@]}
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let "comparisons = $number_of_elements - 1"
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count=1 # Pass number.
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while [ "$comparisons" -gt 0 ] # Beginning of outer loop
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do
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index=0 # Reset index to start of array after each pass.
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while [ "$index" -lt "$comparisons" ] # Beginning of inner loop
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do
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if [ ${Countries[$index]} \> ${Countries[`expr $index + 1`]} ]
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# If out of order...
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# Recalling that \> is ASCII comparison operator
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#+ within single brackets.
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# if [[ ${Countries[$index]} > ${Countries[`expr $index + 1`]} ]]
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#+ also works.
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then
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exchange $index `expr $index + 1` # Swap.
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fi
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let "index += 1" # Or, index+=1 on Bash, ver. 3.1 or newer.
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done # End of inner loop
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# ----------------------------------------------------------------------
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# Paulo Marcel Coelho Aragao suggests for-loops as a simpler altenative.
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#
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# for (( last = $number_of_elements - 1 ; last > 0 ; last-- ))
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## Fix by C.Y. Hunt ^ (Thanks!)
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# do
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# for (( i = 0 ; i < last ; i++ ))
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# do
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# [[ "${Countries[$i]}" > "${Countries[$((i+1))]}" ]] \
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# && exchange $i $((i+1))
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# done
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# done
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# ----------------------------------------------------------------------
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let "comparisons -= 1" # Since "heaviest" element bubbles to bottom,
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#+ we need do one less comparison each pass.
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echo
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echo "$count: ${Countries[@]}" # Print resultant array at end of each pass.
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echo
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let "count += 1" # Increment pass count.
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done # End of outer loop
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# All done.
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exit 0
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