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Practice questions on Loop loop loop

Level 1

1.

Take 10 integers from keyboard using loop and print their average value on the screen.

import java.util.Scanner;
class Ans{
  public static void main(String[] args){
    Scanner s = new Scanner(System.in);
    int sum = 0;
    for(int i = 0; i<10;i++){
      System.out.println("Enter a number");
      sum = sum+s.nextInt();
    }
    System.out.println("Sum is "+sum);
  }
}

2.

Print the following patterns using loop :
a.
*
**
***
****
b.
   *  
 *** 
*****
 *** 
   *  
c.
1010101
 10101 
  101  
   1   


3.

Print multiplication table of 24, 50 and 29 using loop.

class Ans{
  public static void main(String[] args){
    for(int i = 1; i<=10;i++){
      System.out.println("24 * "+i+"\t=\t"+(24*i));
    }
  }
}

4.

Print ASCII values and their equivalent characters. ASCII value vary from 0 to 255.


5.

Factorial of any number n is represented by n! and is equal to 1*2*3*....*(n-1)*n. E.g.-
4! = 1*2*3*4 = 24
3! = 3*2*1 = 6
2! = 2*1 = 2
Also,
1! = 1
0! = 0
Write a Java program to calculate factorial of a number.

import java.util.Scanner;
class Ans{
  public static void main(String[] args){
    Scanner s = new Scanner(System.in);
    System.out.println("Enter a number");
    int x = s.nextInt();
    int fact  =  1;
    for(int i = x; i>=1 ;i--){
      fact = fact*i;
    }
    System.out.println("Factorial is "+fact);
  }
}

6.

Write a program to find greatest common divisor (GCD) or highest common factor (HCF) of given two numbers


7.

Take integer inputs from user until he/she presses q ( Ask to press q to quit after every integer input ). Print average and product of all numbers.

import java.util.*;

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

String choice = "";

int sum = 0;
int product = 1;
int count = 0;
Scanner input = new Scanner(System.in);

while(!choice.equals("q")){
    System.out.println("Enter a number or q to quit");
    choice = input.next();

    if(!choice.equals("q")){
        int number = Integer.parseInt(choice);
        sum = sum+number;
        product = product*number;
        count++;
    }
} 

System.out.println("Product is: "+product+"\nAverage is: "+((float)sum/count));

}
}

8.

Write an infinite loop.
A inifinte loop never ends. Condition is always true.


Level 2

1.

Take as input a fraction in the form a/b. Convert the same into lowest terms and print. (Lowest terms examples 3/12 = 1/4).

import java.util.*;

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

    int num;
    int den;

    Scanner input = new Scanner(System.in);

    System.out.println("Enter numerator");
    num = input.nextInt();
    System.out.println("Enter denominator");
    den = input.nextInt();

    //calculating HCF
    int a,b,gcd,t;
    if(num>den){
      a = num;
      b = den;
    }
    else{
      b = num;
      a = den;
    }
    while (b != 0){
      t = b;
      b = a % b;
      a = t;
    }
    gcd = a;

    System.out.println("In lowest form = "+num/gcd+"/"+den/gcd);
  }
}

2.

Calculate the sum of digits of a number given by user. E.g.-
INUPT : 123        OUPUT : 6
INUPT : 12345        OUPUT : 15


3.

A three digit number is called Armstrong number if sum of cube of its digit is equal to number itself.
E.g.- 153 is an Armstrong number because (13)+(53)+(33) = 153.
Write all Armstrong numbers between 100 to 500.

class Ans{
  public static void main(String[] args) {
    for(int i=1;i<=500;i++){
      int sum = 0;
      int t = i;
      while(t!=0){
        sum = sum+((t%10)*(t%10)*(t%10));
        t = t/10;
      }
      if(sum==i){
        System.out.println(i);
      }
    }
  }
}

4.

Write a program to print all prime number in between 1 to 100.


5.

Write a program to find prime factor of a number.
If a factor of a number is prime number then it is its prime factor.

import java.util.*;

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

    Scanner input = new Scanner(System.in);

    int x;

    System.out.println("Enter the number");
    x = input.nextInt();

    System.out.println("Prime factors of "+x+" are:");

    for(int i=2;i<=x;i++){
      //checking for factor
      if(x%i==0){
        //checking if i is prime or not
        int p = 0;
        for(int j=2;j<i;j++){
          if(i%j==0){
            //i is not prime
            p++;
            break;
          }
        }
        if(p==0){
          //if p is 0
          //then i is prime
          System.out.println(i);
        }
      }
    }
  }
}

6.

Write a program in java to find the sum of the even and odd digits of the number which is given as input.


Level 3

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