added double jump and sitting state

term1/seminar01_overload/05_add_price/add_price.cpp

@@ -0,0 +1,20 @@
+#include <iostream>
+
+using std::cout, std::endl;
+
+struct Book {
+    char title[100];
+    int pages;
+    float price;
+};
+
+void addPrice(Book& b, float x) {
+    b.price += x;
+}
+
+int main() {
+    Book b = {"One Hundred Years of Solitude", 456, 1200};
+    float x = 15.6;
+    addPrice(b, x);
+    cout << b.price << endl;
+}