Recursion

README.md

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+# AlgorithmsAndDataStructures
+Recursion
+1. Написать программу по возведению числа в степень с помощью рекурсии.
+2. Написать программу «Задача о рюкзаке» с помощью рекурсии.

src/algorithmsAndDataStructures/Backpack.java

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+package algorithmsAndDataStructures;
+
+public class Backpack {
+    private Item[] item;
+
+    public Backpack(Item[] item) {
+        this.item = item;
+
+    }
+
+    public int put(int i, int weight) {
+        if (i < 0) {
+            return 0;
+        }
+        if (item[i].getWeight() > weight) {
+            return put(i - 1, weight);
+
+        } else return Math.max(put(i - 1, weight),
+                put(i - 1, weight - item[i].getWeight()) + item[i].getPrice());
+    }
+}

src/algorithmsAndDataStructures/Item.java

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+package algorithmsAndDataStructures;
+
+public class Item {
+    private int weight;
+    private int price;
+
+    public Item(int weight, int price) {
+        this.weight = weight;
+        this.price = price;
+    }
+
+    public int getWeight() {
+        return weight;
+    }
+
+    public int getPrice() {
+        return price;
+    }
+}

src/algorithmsAndDataStructures/Main.java

@@ -3,6 +3,57 @@
 public class Main {
 
     public static void main(String[] args) {
-	// write your code here
+
+        doTask2();
+//        System.out.println(recursFib(5));
+//        System.out.println(recurs(5));
+//        System.out.println(doTask(5, -2));
+//        System.out.println(recTriangleNum(5));
+    }
+
+    public static double doTask1(double x, int y) {
+        if (y == 1) {
+            return x;
+        }
+        if (y == 0) {
+            return 1;
+        }
+        if (y < 0) {
+            return 1 / x * doTask1(x, ++y);
+        }
+        return doTask1((x * x), y - 1);
+    }
+
+    public static void doTask2() {
+        Item[] items = new Item[]{
+                new Item(5, 7),
+                new Item(10, 7),
+                new Item(3, 2)
+        };
+        Backpack backpack = new Backpack(items);
+        int sizeBag = 10;
+        System.out.println(backpack.put(items.length - 1, sizeBag));
+    }
+
+    public static int recurs(int n) {
+        if (n == 1) {
+            return n;
+        }
+        return recurs(n - 1) * n;
+    }
+
+    public static int recursFib(int n) {
+        if (n < 3) {
+            return 1;
+        }
+        return recursFib(n - 1) + recursFib(n - 2);
+    }
+
+    public static int recTriangleNum(int n) {
+        System.out.println(n);
+        if (n == 1) {
+            return 1;
+        }
+        return recTriangleNum(n - 1) + n;
     }
-}
+}