Examples 2

1. This is a script that calculates the Fibonacci numbers, using an iterative algorithm:

   fibo.sh

   #!/bin/bash
   
   N=$1
   if [[ -z $N ]]; then
       echo "Usage: $0 <n>" >&2
       exit 1
   fi
   
   [[ $N == 0 ]] && echo 0 && exit
   [[ $N == 1 ]] && echo 1 && exit
   
   f0=0
   f1=1
   for ((i=1; i<N; i++)); do
       fib=$((f0 + f1))
       f0=$f1
       f1=$fib
   done
   echo $f1

   vim fibo.sh

   ./fibo.sh

   for i in {0..10}; do ./fibo.sh $i; done

   ./fibo.sh 100

2. This is a script that solves the problem of Towers of Hanoi, using a recursive algorithm:

   hanoi.sh

   #!/bin/bash
   
   solve_hanoi() {
       local disks=$1 src=$2 dst=$3 aux=$4
       if ((disks > 0)); then
           solve_hanoi $((disks - 1)) $src $aux $dst
           echo "move $src --> $dst"
           ((nr_moves++))
           solve_hanoi $((disks - 1)) $aux $dst $src
       fi
   }
   
   read -p "Towers of Hanoi. How many disks? " disks
   
   nr_moves=0     # start with no moves
   solve_hanoi $disks 'src' 'dst' 'aux'
   
   echo "It took $nr_moves moves to solve Towers for $disks disks."

   vim hanoi.sh

   ./hanoi.sh <<< 0

   ./hanoi.sh <<< 1

   ./hanoi.sh <<< 2

   ./hanoi.sh <<< 3

   ./hanoi.sh <<< 4

   ./hanoi.sh <<< 5

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