Unique Number
Unique Number : A number is said to be a Unique number if it is a positive integer (without leading zeros) with no duplicate digits.
For example : 7, 135, 214 are all unique numbers whereas 33, 3121, 300 are not.
Input    : 142
Output : It is a Unique Number
Input    :0125
Output : It is not a Unique Number
Input    : 131
Output : It is not a Unique Number
Algorithm and Program given below :-
Algorithm :-
Input number as a string
Store the length of the string in a variable
Using if statement first check if at 1st position (i.e. at 0th position of the string) '0' is present or not
If '0' is present than display "Number is not Unique"
Else using for loop extract each character and store it in an Array by converting the character into integer using type cast operator
After storing all the digits in the array
Use another for loops to check whether the number contains any duplicate digits.
If duplicate digits are found than display "Number is not Unique"
Else display "Number is Unique"
Compile and run the program
Program :-
import java.io.*; import java.util.*; class Unique {    public static void main(String args[])    {        Scanner in = new Scanner(System.in);        int ar[]=new int[100]; //array for storing and comparing digits        int i,j,k=0,a=0,l;        String str;        char ch;        System.out.println("Enter Number ");        str= in.nextLine(); //Input number as a string        l= str.length(); // storing length of string        if(str.charAt(0)=='0') // if 0 is leading the number        {            System.out.println("It is not a Unique Number : " +str);        }        else        {            for(i=0;i<l;i++)            {                ch= str.charAt(i);                ar[a]=(int)ch; //storing each digit of the number                a++;            }            for(i=0;i<(a-1);i++)            {                for(j=i;j<(a-1);j++)                {                    if(ar[i]==ar[j+1]) // comparing digits                    {                        k=1; // if the digit are same than changing value of k to 1                        break; //using break statement to jump out of inner for loop                    }                }                if(k==1)                {                    break; //using break statement to jump out of outer for loop                }            }            if(k==1) // if k is equal to 1            {                System.out.println("It is not a Unique Number : " +str);            }            else            {                System.out.println("It is a Unique Number : "+str);            }        }    } // end of main method } // end of class
Note : The program is written in the easiest way possible so try to understand it. If you face any problem in understanding this program than feel free to contact/comment.
Source Code : Click here
Program Video : Watch now
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