JAVA-MATHS-101

Question 1

Define Permutation & Combination in one Line with formula

Answer 1

Perm : When no repitetion ; n!

Comb: When repetion is allowed ;

Question 2

Write a Program to find Permutation & Combination?

Answer 2

import java.util.Date;
import java.util.*;

public class HelloWorld {
    public static void main(String[] args) {

     char elements[] = {'R','O','O','T'};

     int noOfUniqueElements = getUniqueElements(elements);   //case of PErutation

     int noOfElements = elements.length;  // case Of Combination
     int noOFSlots = 3;

  System.out.println(doPerm(noOfElements, noOFSlots));

  System.out.println(doComb(noOfElements, noOFSlots));
}

private static int getUniqueElements(char elements[]){

   // to do 

   return elements.length;

}

private static int doPerm(int noOFElements, int noOFSlots){
  int perms = noOFElements;
  while(noOFSlots > 1){

        noOFElements = noOFElements - 1;
        perms = perms * noOFElements;    // mind that the perms should not bemultiplied to perms
                                                // and also the noOfElements-1 wont work

    noOFSlots--;
  }

  return perms;
}

private static int doComb(int noOFElements, int noOFSlots){
  int perms = 1;
  while(noOFSlots > 0){

    perms = perms * noOFElements;   
    noOFSlots--;
  }

  return perms;
}

}

Question 3

What strategy will you apply to find the non repeated unique number be formed inbetween 100 & 1000. Where the numbers used are 0-6 and no duplicates must come in number generations?

Answer 3

This is a problem of permutation

import java.util.Date;

public class HelloWorld {
    public static void main(String[] args) {
        int noOfElements = 5; // as the 0-6 , but the hundreath place wil be taken 
        int noOSlots = 3;

    int perms = 5; // as the very first or the hundreath place wont have 0

    while(noOSlots > 1){

      perms = perms * noOfElements;

      noOfElements--;

    noOSlots--;  
    }   

    System.out.println(perms);

}

}