day 2 commit & changed day 1 filenames

D2_factorial.cpp

@@ -0,0 +1,19 @@
+#include <iostream>
+
+int factorial(int n) {
+    if (n <= 0) {
+        return -1;
+    } else if (n > 1) {
+        return n * factorial(n - 1); //n * n-1 * n-2....
+    } else return 1;
+}
+
+int main() {
+    int n;
+
+    std::cout << "Enter n to do n!: ";
+    std::cin >> n;
+
+    std::cout << "Ans: " << factorial(n) << std::endl;
+    return 0;
+}

D2_looping.cpp

@@ -0,0 +1,50 @@
+#include <iostream>
+#include <vector>
+
+int main() {
+    std::vector<int> list; //= {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
+    int arr[10]; //= {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
+
+    //initialize vector
+    for (int i = 0; i < 10; i++) {
+        list.push_back(i);
+    }
+
+    //initialize array
+    for (int i = 0; i < 10; i++) {
+        arr[i] = i;
+    }
+
+    int n;
+
+    std::cout << "Enter number: ";
+    std::cin >> n;
+
+    //standard for loop
+    for (int i = 0; i < n; i++) {
+        std::cout << list.at(i%10) << " ";
+    }
+    std::cout << std::endl;
+
+    //while loop
+    int j = 0;
+    while (j < n) {
+        std::cout << j << " ";
+        j++;
+    }
+    std::cout << std::endl;
+
+    //range based loop w/ vector
+    for (int k : list) {
+        std::cout << k << " ";
+    }
+    std::cout << std::endl;
+
+    //range based loop w/ array
+    for (int l : arr) {
+        std::cout << l << " ";
+    }
+    std::cout << std::endl;
+
+    return 0;
+}

D2_power.cpp

@@ -0,0 +1,30 @@
+#include <iostream>
+
+int power(int n, int e) {
+    if (n < 0 || e < 0) return -1;
+    else if (e > 0) return n * power(n, e - 1);
+    else return 1;
+}
+
+int main() {
+    int n, e;
+
+    std::cout << "Enter number: ";
+    std::cin >> n;
+    std::cout << "Enter exponent: ";
+    std::cin >> e;
+
+    std::cout << "Ans: " << power(n, e) << std::endl;
+    return 0;
+
+    /*
+     * Example:
+     *
+     *      5^4
+     *
+     *              5 * 5^3 =
+     *          5 * 5 * 5^2 =
+     *      5 * 5 * 5 * 5^1 =
+     *  5 * 5 * 5 * 5 * 5^0 = 625
+     */
+}