Question

Use the IO module for all inputs and outputs. Sevens are considered lucky numbers. Your task is to count the number of sevens that appear within a range of integer numbers. Your solution should make use of looping constructs.

Ask the user for the following information, in this order:

The lower end of the range

The upper end of the range

Compute and then output the number of sevens that appear in the sequence from lower end to upper end (inclusive). Hint: Some numbers have more than 1 seven, and not every 7 appears in the ones place. Hint2: Nested loops are helpful On error output -1 using the IO module.

USE IO.readint(), IO.readDouble()...etc.

NONE of the scan.next

Answer 1

I have given the implementation of Java program to count the lucky numbers between a range.

Copy the below java file in your editor and test.

DigitCount.java

import java.util.Scanner;

public class DigitCount {

//static function to calc the luckynum count

static int luckyNumCount(int min, int max, int luckyNum) {

// initialize result

int result = 0;

// One by one compute sum of digits

// in every number from 1 to n

for (int x = min; x <= max; x++)

//sum all the luckynums

result += calcCount(x, luckyNum);

return result;

}

//get count of luckynum for the given num (ex :{7-1, 17-1, 77-2, 777-3})

static int calcCount(int x, int luckyNum) {

int count = 0, r;

while (x > 0) {// repeat till the x becomes 0

r = x % 10;// get remainder of x into r

x = x / 10; // get quotient of x into x

if (r == luckyNum)

count++;

}

return count;

}

// Driver Program

public static void main(String args[]) {

//luckynum to be counted

int luckyNum = 7;

Scanner s = new Scanner(System.in);

System.out.print("Enter the lower end value of the range : ");

int min = s.nextInt();

System.out.print("Enter the upper end value of the range : ");

int max = s.nextInt();

System.out.println("Count of numbers from " + min + " to " + max + " that have " + luckyNum

+ " as a digit is " + luckyNumCount(min, max, luckyNum));

}

}

Output :

Enter the lower end value of the range : 1
Enter the upper end value of the range : 80
Count of numbers from 1 to 80 that have 7 as a digit is 18

1 import java.util.Scanner; 2 3 public class DigitCount 4 //static function to cals the luckynum count 5 static int luckyNumCount(int min, int max, int luckyNum) //initialize result int result-; 6 7 8 9 10 // One by one compute sum of digits // in every number from 1 to n for (int x min; x <= max; x++) //sum al1 result += the calcCount(x, 12 luckyNum); return result; 16 17 18 I/get count of luckynum for the given num (ex :17-1, 17-1, 77-2, 777-3)) 19 static int calcCount (int x, int luckyNum) { 20 21 int count -0, r; while (x > 0) // repeat till the x becomes r·. % 10; // get remainder of x into r x х / 10; // get quotient of x into x if (r-- luckyNum) 23 25 26 count+t 27 return count; 28 29 30 31 public static void main(String args[]) // Driver Program //luckynum to be counted int luckyNum = 7; Scanner s-new Scanner(System.in); System.out.prin( "Enter the lower end value of the range") int min = s.nextInt(); Sustem.out.nrint( "Fnter the unner end value of the range: 34 35 36

«terminated> DigitCount Java Application C:\Program Files Javallrel .8.0 144 bin yavaw.exe (28-Feb-2018,6:49:2 Enter the lower end value of the range 1 Enter the upper end value of the range 80 Count of numbers from 1 to 80 that have 7 as a digit is 18