Question

Write code in Java. In this step, functions and methods are synonymous. You may assume that strings only contain uppercase letters A through Z. 1. Write a function as follows: o Receive a string as a parameter. o Count the length of the string Count the occurrences of each distinguishable symbol in the string (use an array or map/dictionary). o Divide the factorial of the length by the product of the factorials of the occurrences. o Return the quotient as the integer result. The point of this function is to find the result only by using the formulas for permutations. P(n,r) = n! (n – r)! For example, for AAAB, the function counts that the string length is 4, that A occurs 3 times, and that B occurs 1 time, then divides 4! By 3! And 1! and returns the quotient, which is 4.

Answer 1

program logic:

• We will use a hashmap to store the number of occurences of each distinct character. To do this, loop through each character of string, if the character is already present in the hashmap, then increment its value, otherwise add it to hashmap and set its value to 1.
• Then , inorder to find the quotient, first find the factorial of length of string and store in a variable name numerator.
• Then, loop throgh each value in hashmap and multiply it to denominator.
• divide the numerator by denominator and return the value.

program:

import java.util.*;
import java.io.*;

public class Test {
   public static int factorial(int n){
       int prod = 1;
       for(int i = 1; i<=n; i++)
           prod *= i;
       return prod;
   }
   public static int countOccurences(String str){
       HashMap<Character, Integer> charCountMap = new HashMap<Character, Integer>();
       char[] strArray = str.toCharArray();
       for(char c: strArray){
           if(charCountMap.containsKey(c))
               charCountMap.put(c, charCountMap.get(c)+1);
           else
               charCountMap.put(c,1);
       }
       int numer = factorial(str.length());
       int denom = 1;
       for(int value: charCountMap.values()){
           denom *= factorial(value);
       }
       return numer/denom;
   }

   public static void main(String[] args){
       String str = "AAAB";
       int permute = countOccurences(str);
       System.out.println("Return value: "+permute);
   }
}

output:

• Note that we are using string as "AAAB" . you may change this value

Return value: 4