replace every second value in a sequence with special character '*'

Question

Let's take Input from user as 9. So the Fibonacci series upto 9 is as follow's   0,1,1,2,3,5,8,13,21
Expected Output : 0,*,1,*,3,*,8,*,21
Below is the following code which i work around to implement logic
UserInput=9 
a=0 
b=1

echo "The Fibonacci series is  : "

for (( i=0; i<UserInput; i++ )) 
do
    if [ $i -eq 2 ]
    then 
        echo -n "$a "
        sn=$((a + b)) 
        a=$b 
        b=$sn 
    fi 
done

AdminBee · Accepted Answer

Mandatory awk-based solution (where for simplicity I will assume n>2): awk -v n=9 'BEGIN{q=1; printf "0,*,"; for (i=2;i2): printf "0,*," loop from 2 to n-1 and calculate the Fibonaccy number s as sum of the two previous ones q and r, and update q and r print either * if i is even, or the current Fibonacci number s if it is not (i%2?"*":s) and print either a , or a newline after that, depending on whether we have reached the end of the loop (i==n-1) or not.

FedonKadifeli · Answer

The closest to your code, using Bash and arithmetic operators is this:
#!/bin/bash
let UserInput=9 
let a=0 
let b=1
echo -n "The Fibonacci series is: 0"
for (( i=1; i<UserInput; i++ )) ; do
  let sn=a+b
  let a=b
  let b=sn
  if (( i % 2 == 0 )) ; then 
    echo -n ",$a"
  else
    echo -n ",*"
  fi 
done
echo

In the if statement you have to use the % modulo (remainder) operator. Using it you can test whether i is divisible to two (i.e. an even number) and print the value of $a or print a * accordingly.
The output will be:
The Fibonacci series is: 0,*,1,*,3,*,8,*,21

To change the script, so that it gets the number of steps from its argument, please modify the first line of the script like this:
let UserInput="$1"

replace every second value in a sequence with special character '*'

2 Answers

Add your own answers!

Ask a Question