/**
 * Demos of recursion.
 * @author Sean Barker
 */
public class Recursion {

    // iterative (not recursive) factorial implementation
    public static int fact_iter(int n) {
        int result = 1;
        for (int i = 1; i <= n; i++) {
            result *= i;
        }
        return result;
    }

    // recursive factorial implementation
    public static int fact(int n) {
        if (n == 0) { // base case
            return 1;
        } else { // recursive case
            return fact(n - 1) * n;
        }
    }

    // raise base to a power
    public static double exp(double base, int power) {
        if (power == 0) {
            return 1;
        } else {
            return base * exp(base, power - 1);
        }
    }

    // find the nth fibonacci number
    public static int fib(int n) {
        if (n == 0 || n == 1) {
            return 1;
        } else {
            return fib(n - 1) + fib(n - 2);      
        }
    }

    // find the length of a string
    public static int strlen(String s) {
        if (s.equals("")) {
            return 0;
        } else {
            return 1 + strlen(s.substring(1));
        }
    }

    // return the reverse of a string
    public static String reverse(String s) {
        if (s.equals("")) {
            return "";
        } else {
            return reverse(s.substring(1)) + s.charAt(0);
        }
    }

    // return a string that is the given string with all
    // occurrences of the character c removed
    public static String removeChar(String s, char c) {
        if (s.equals("")) {
            return s;
        }
        char firstChar = s.charAt(0);
        if (firstChar == c) {
            return removeChar(s.substring(1), c);
        } else {
            return firstChar + removeChar(s.substring(1), c);
        }
    }

}