Question

IN PYTHON

Given a string with duplicate characters in it. Write a program to generate a list that only contains the duplicate characters. In other words, your new list should contain the characters which appear more than once.

Suggested Approach

• Used two nested for loops.
• The first for loop iterates from 0 to range(len(input_str)).
• The second for loop iterates from first_loop_index + 1 to range(len(input_str)). The reason you want to start at first_loop_index + 1 in the nested inner loop is that the outer loop already checks the current character. In the nested inner loop, you want to check the remaining characters in the input string.
• If the current character of the outer loop matches the character of the nested loop AND the character is not already IN the duplicate list, append it to the list
• nhantran

  Sample Output 1

  List of duplicate chars: ['n', 'a']

  Sample Input 2

  pneumonoultramicroscopicsilicovolcanoconiosis

  Sample Output 2

  List of duplicate chars: ['p', 'n', 'u', 'm', 'o', 'l', 'r', 'a', 'i', 'c', 's']

  Sample Input 3

  pulchritudinous

  Sample Output 3

  List of duplicate chars: ['u', 'i']

  Sample Input 4

  orden

  Sample Output 4

  List of duplicate chars: []

Answer 1

Here is the Python code to the given question.

Four sample outputs are added at the end.

Code:

inputString=input("Enter the string:")    #stores input string entered by the user

duplicateList=[]    #creates empty list to store duplicate chars

for i in range(len(inputString)):     #runs loop from i=0 to last element of string
    
    for j in range(i+1,len(inputString)):      #runs loop from j=i to last element of string
        
        if inputString[i]==inputString[j] and inputString[i] not in duplicateList:     #checks if two characters are equal and duplicate char is not already present in duplicateList
            
            duplicateList.append(inputString[i])      #append the present char to duplicateList
            
            break      #exit from inner loop
    
print("List of duplicate chars: ",duplicateList)     #prints the duplicate list

Sample Output-1:

Sample Output-2:

Sample Output-3:

Sample Output-4: