different loops question answer

loops/Ans1.java

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+package language.Java.loops;
+import java.util.Scanner;
+public class Ans1 {
+
+    public static void main(String[] args) {
+        // 1. Write a C program to print all natural numbers from 1 to n. - using while loop
+        Scanner sc = new Scanner(System.in);
+        int n = sc.nextInt();
+        int i = 1;
+        while (i<=n) {
+            System.out.println(i++);
+        }
+    }
+}

loops/Ans10.java

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+package language.Java.loops;
+
+import java.util.Scanner;
+
+public class Ans10 {
+    public static void main(String[] args) {
+        // 10. Write a C program to count number of digits in a number.
+
+        Scanner sc = new Scanner(System.in);
+        int number = sc.nextInt();
+        int count = 0;
+       while (!(number == 0)) {
+           count++;
+           number = number/10;
+            }
+            System.out.println(count);
+       }
+    }

loops/Ans11.java

@@ -0,0 +1,27 @@
+package language.Java.loops;
+
+import java.util.Scanner;
+
+public class Ans11 {
+    public static void main(String[] args) {
+        // 11. Write a C program to find first and last digit of a number.
+
+        Scanner sc = new Scanner(System.in);
+        int number = sc.nextInt();
+        int count = 0;
+        int number1 =number;
+        int firstNo = number%10;
+        System.out.println("first no is "+firstNo);
+
+        while (!(number1 == 0)) {
+           count++;
+           number1 = number1/10;
+            }
+
+            for (int i = 1; i < count ; i++) {
+                number = number/10;
+            }
+         int lastNo = number;
+         System.out.println("last no is "+lastNo);
+       }
+    }

loops/Ans12.java

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+package language.Java.loops;
+
+import java.util.Scanner;
+
+public class Ans12 {
+    public static void main(String[] args) {
+        // 12. Write a C program to find sum of first and last digit of a number
+        Scanner sc = new Scanner(System.in);
+        int number = sc.nextInt();
+        int count = 0;
+        int number1 =number;
+        int firstNo = number%10;
+        System.out.println("first no is "+firstNo);
+
+        while (!(number1 == 0)) {
+           count++;
+           number1 = number1/10;
+            }
+
+            for (int i = 1; i < count ; i++) {
+                number = number/10;
+            }
+         int lastNo = number;
+         System.out.println("last no is "+lastNo);
+
+         System.out.println("sum is "+(lastNo+firstNo));
+    }
+}

loops/Ans13.java

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+package language.Java.loops;
+
+import java.util.Scanner;
+
+public class Ans13 {
+    public static void main(String[] args) {
+        // 13. Write a C program to swap first and last digits of a number.
+
+        // int n, f, l, r = 0, tmp, swap, c, d;
+        Scanner s = new Scanner(System.in);
+        System.out.println("Enter the number:\n");
+        // n = s.nextInt();
+        // tmp = n;
+        // l = n % 10;
+        // while (n > 10) {
+        //     n = n / 10;
+        // }
+        // f = n;
+        // n = tmp / 10;
+        // while (n > 10) {
+        //     c = n % 10;
+        //     r = r * 10 + c;
+        //     n = n / 10;
+        // }
+        // swap = l;
+        // while (r > 0) {
+        //     d = r % 10;
+        //     swap = swap * 10 + d;
+        //     r = r / 10;
+        // }
+        // swap = swap * 10 + f;
+        // System.out.println("After swap:" + swap);
+
+
+        int number = s.nextInt();
+        int temp = number;
+
+        int lastNumber = number%10;
+        System.out.println("Last Number is "+lastNumber);
+
+        int count = 0;
+
+        while (number>10) {
+            count++;
+            number= number/10;
+        }
+        int firstnumber = number;
+        System.out.println("First Number is "+firstnumber);
+
+        number = temp;
+        number = number/10;
+        int middleNumber =0;
+         middleNumber = middleNumber + number% (int)Math.pow(10, count -1);
+        System.out.println("middle number is "+middleNumber);
+
+        int swpno = (lastNumber*(int)Math.pow(10, count)) + (middleNumber*10) + firstnumber;
+
+        System.out.println(swpno);
+
+    }
+}

loops/Ans14.java

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+package language.Java.loops;
+
+import java.util.Scanner;
+
+public class Ans14 {
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+
+        int number = sc.nextInt();
+        int sum = 0;
+        while (number > 0) {
+           int last = number%10;
+           number = number/10;
+           sum = sum +last;
+        }
+        System.out.println("the sum of digits of a number is "+sum);
+    }
+}

loops/Ans15.java

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+package language.Java.loops;
+
+import java.util.Scanner;
+
+public class Ans15 {
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+
+        int number = sc.nextInt();
+        int temp = number;
+        int product = 1 ;
+        int lastnumber = 0;
+        while (number >0) {
+
+            lastnumber = number%10;
+
+            product *= lastnumber;
+
+            number/=10;
+        }
+       number = temp;
+        System.out.println("The product of digit of  "+number+" is "+product);
+
+
+
+    }
+}
+

loops/Ans16.java

@@ -0,0 +1,29 @@
+package language.Java.loops;
+
+import java.util.Scanner;
+
+public class Ans16 {
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+        int number = sc.nextInt();
+
+        int reverse=0,num=0;
+
+
+        while (number >0) {
+
+
+             num = number%10;
+
+             reverse = reverse+ num;
+
+            reverse *=10;
+
+            number = number/10;
+
+        }
+        reverse /=10;
+        System.out.println("The reverse number is "+reverse);
+
+    }
+}

loops/Ans17.java

@@ -0,0 +1,32 @@
+package language.Java.loops;
+
+import java.util.Scanner;
+
+public class Ans17 {
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+        int number = sc.nextInt();
+        int temp = number;
+        int reverse=0,num=0;
+
+
+        while (number >0) {
+
+
+             num = number%10;
+
+             reverse = reverse+ num;
+
+            reverse *=10;
+
+            number = number/10;
+
+        }
+        reverse /=10;
+        number = temp;
+        if (number == reverse) {
+            System.out.println("it is a palindrome no");
+        }
+        else System.out.println("it is not a palindrome no ");
+    }
+}

loops/Ans18.java

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+package language.Java.loops;
+import java.util.Scanner;
+
+public class Ans18 {
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+        int number = sc.nextInt();
+
+
+
+        int one = 0;
+        int two = 0;
+        int three = 0;
+        int four = 0;
+        int five = 0;
+        int six = 0;
+        int seven = 0;
+        int eight = 0;
+        int nine = 0;
+        int zero = 0;
+
+        while (number>0){
+            int lastnumber =number%10;
+
+            switch (lastnumber) {
+                case 1:
+                     one += 1;
+                    break;
+                case 2: 
+                     two += 1;
+                    break;
+
+                case 3: 
+                     three += 1;
+                    break;
+                case 4: 
+                 four += 1;
+                break;
+                case 5: 
+                 five += 1;
+                break;
+                case 6: 
+                 six += 1;
+                break;
+                case 7: 
+                 seven += 1;
+                break;
+                case 8: 
+                 eight += 1;
+                break;
+                case 9: 
+                 nine += 1;
+                break;
+                case 0: 
+                 zero += 1;
+                break;
+            }
+
+            number/=10;
+
+
+        }
+
+        System.out.println(" one  "+one );
+        System.out.println(" two "+two );
+        System.out.println(" three "+three );
+        System.out.println(" four "+four );
+        System.out.println(" five "+five );
+        System.out.println(" six "+six );
+        System.out.println(" seven "+seven );
+        System.out.println(" eight "+ eight);
+        System.out.println(" nine "+ nine);
+        System.out.println("  zero"+zero );
+
+
+    }}

loops/Ans19.java

@@ -0,0 +1,10 @@
+package language.Java.loops;
+import java.util.Scanner;
+
+public class Ans19 {
+    public static void main(String[] args) {
+        Scanner sc = new Scanner(System.in);
+
+        // same as ans 18
+    }
+}

loops/Ans2.java

@@ -0,0 +1,18 @@
+package language.Java.loops;
+
+import java.util.Scanner;
+
+public class Ans2 {
+    public static void main(String[] args) {
+        // 2. Write a C program to print all natural numbers in reverse (from n to 1). - using while loop
+        Scanner sc = new Scanner(System.in);
+        int n = sc.nextInt();
+        while (n>1) {
+
+
+            System.out.println(n--);
+
+        }
+        System.out.println(n);
+    }
+}