Recursion in One Shot | Theory + Question Practice + Code | Level 1 - Easy

JAVA Recursion Class 1 (Codes)

Q1. Print numbers from 5 to 1.

public static void printNumbers(int n) {
if(n == 0) {
return;
}
System.out.println(n);
printNumbers(n-1);
}

Q2. Print numbers from 1 to 5.

public static void printNumbers(int n) {
if(n == 6) {
return;
}
System.out.println(n);
printNumbers(n+1);
}

Q3. Print the sum of first n natural numbers.

class Recursion1 {
public static void printSum(int n, int sum) {
if(n == 0) {
System.out.println(sum);
return;
}
sum += n;
printSum(n-1, sum);
}
public static void main(String args[]) {
printSum(5, 0);
}
}

Q4. Print factorial of a number n.

class Recursion1 {
public static void printFactorial(int n, int fact) {
if(n == 0) {
System.out.println(fact);
return;
}
fact *= n;
printFactorial(n-1, fact);
}
public static void main(String args[]) {
printFactorial(5, 1);
}
}

Q5. Print the fibonacci sequence till nth term.

class Recursion1 {
public static void printFactorial(int a, int b, int n) {
if(n == 0) {
return;
}
System.out.println(a);
printFactorial(b, a+b, n-1);
}
public static void main(String args[]) {
printFactorial(0, 1, 5);
}
}

Q6. Print x^n (with stack height = n)

class Recursion1 {
public static int printPower(int x, int n) {
if(n == 0) {
return 1;
}
if(x == 0) {
return 0;
}
int x_ = printPower(x, n-1);
int xn = x * x_;
return xn;
}
public static void main(String args[]) {
int x = 2, n = 5;
int output = printPower(x, n);
System.out.println(output);
}
}

Q7. Print x^n (with stack height = logn)

class Recursion1 {
public static int printPower(int x, int n) {
if(n == 0) {
return 1;
}
if(n % 2 == 0) {
return printPower(x, n/2) * printPower(x, n/2);
}
else {
return x * printPower(x, n/2) * printPower(x, n/2);
}
}
public static void main(String args[]) {
int x = 2, n = 5;
int output = printPower(x, n);
System.out.println(output);
}
}