Recursion

title: Recursion in Java description: Recursive programming concepts aur examples

Function khud ko call kare = Recursion. Base case zaruri hai (infinite loop rokne ke liye).

Structure

java exampleWoHoTech

returnType function(params) {
    // Base case — recursion rokta hai
    if (baseCondition) return baseValue;
    // Recursive case — smaller problem
    return function(smallerParams);
}

Classic Examples

Factorial

java exampleWoHoTech

long factorial(int n) {
    if (n <= 1) return 1;       // Base case
    return n * factorial(n - 1); // Recursive case
}
// factorial(5) = 5 * factorial(4) = 5 * 4 * 3 * 2 * 1 = 120

Fibonacci

int fib(int n) { if (n <= 1) return n; // Base cases: fib(0)=0, fib(1)=1 return fib(n - 1) + fib(n - 2); // O(2ⁿ) — very slow! } // Memoization (O(n)) int fibMemo(int n, int[] memo) { if (n <= 1) return n; if (memo[n] != 0) return memo[n]; memo[n] = fibMemo(n-1, memo) + fibMemo(n-2, memo); return memo[n]; }

Binary Search (Recursive)

int binarySearch(int[] arr, int target, int lo, int hi) { if (lo > hi) return -1; int mid = lo + (hi - lo) / 2; if (arr[mid] == target) return mid; if (arr[mid] < target) return binarySearch(arr, target, mid + 1, hi); return binarySearch(arr, target, lo, mid - 1); }

Power (x^n)

java exampleWoHoTech

double power(double x, int n) {
    if (n == 0) return 1;
    if (n < 0) return 1.0 / power(x, -n);
    if (n % 2 == 0) {
        double half = power(x, n / 2);
        return half * half; // O(log n)
    }
    return x * power(x, n - 1);
}

Print all subsets

void subsets(int[] arr, int index, List<Integer> current) { if (index == arr.length) { System.out.println(current); return; } current.add(arr[index]); subsets(arr, index + 1, current); // include current.remove(current.size() - 1); subsets(arr, index + 1, current); // exclude }

title: Recursion in Java description: Recursive programming concepts aur examples

Function khud ko call kare = Recursion. Base case zaruri hai (infinite loop rokne ke liye).

Structure

java exampleWoHoTech

returnType function(params) {
    // Base case — recursion rokta hai
    if (baseCondition) return baseValue;
    // Recursive case — smaller problem
    return function(smallerParams);
}

Classic Examples

Factorial

java exampleWoHoTech

long factorial(int n) {
    if (n <= 1) return 1;       // Base case
    return n * factorial(n - 1); // Recursive case
}
// factorial(5) = 5 * factorial(4) = 5 * 4 * 3 * 2 * 1 = 120

Fibonacci

Binary Search (Recursive)

Power (x^n)

java exampleWoHoTech

double power(double x, int n) {
    if (n == 0) return 1;
    if (n < 0) return 1.0 / power(x, -n);
    if (n % 2 == 0) {
        double half = power(x, n / 2);
        return half * half; // O(log n)
    }
    return x * power(x, n - 1);
}

Recursion

Structure

Classic Examples

Factorial

Fibonacci

Binary Search (Recursive)

Power (x^n)

Print all subsets

Continue learning this concept

Recursion

Structure

Classic Examples

Factorial

Fibonacci

Binary Search (Recursive)

Power (x^n)

Print all subsets

Continue learning this concept