Merge pull request #1452 from shellhub/ProjectEuler

Added Project Euler

DIRECTORY.md

@@ -200,6 +200,10 @@
   * [TowerOfHanoi](https://github.com/TheAlgorithms/Java/blob/master/Others/TowerOfHanoi.java)
   * [WorstFit](https://github.com/TheAlgorithms/Java/blob/master/Others/WorstFit.java)
 
+## ProjectEuler
+  * [Problem01](https://github.com/TheAlgorithms/Java/blob/master/ProjectEuler/Problem01.java)
+  * [Problem02](https://github.com/TheAlgorithms/Java/blob/master/ProjectEuler/Problem02.java)
+
 ## Searches
   * [BinarySearch](https://github.com/TheAlgorithms/Java/blob/master/Searches/BinarySearch.java)
   * [InterpolationSearch](https://github.com/TheAlgorithms/Java/blob/master/Searches/InterpolationSearch.java)

ProjectEuler/Problem01.java

@@ -0,0 +1,51 @@
+package ProjectEuler;
+
+/**
+ * If we list all the natural numbers below 10 that are multiples of 3 or 5,
+ * we get 3, 5, 6 and 9. The sum of these multiples is 23.
+ * <p>
+ * Find the sum of all the multiples of 3 or 5 below 1000.
+ * <p>
+ * Link: https://projecteuler.net/problem=1
+ */
+public class Problem01 {
+    public static void main(String[] args) {
+        int[][] testNumber = {
+                {3, 0},
+                {4, 3},
+                {10, 23},
+                {1000, 233168},
+                {-1, 0}
+        };
+
+        for (int[] ints : testNumber) {
+            assert solution1(ints[0]) == ints[1];
+            assert solution2(ints[0]) == ints[1];
+        }
+    }
+
+    private static int solution1(int n) {
+        int sum = 0;
+        for (int i = 3; i < n; ++i) {
+            if (i % 3 == 0 || i % 5 == 0) {
+                sum += i;
+            }
+        }
+        return sum;
+    }
+
+    private static int solution2(int n) {
+        int sum = 0;
+
+        int terms = (n - 1) / 3;
+        sum += terms * (6 + (terms - 1) * 3) / 2;
+
+        terms = (n - 1) / 5;
+        sum += terms * (10 + (terms - 1) * 5) / 2;
+
+        terms = (n - 1) / 15;
+        sum -= terms * (30 + (terms - 1) * 15) / 2;
+
+        return sum;
+    }
+}

ProjectEuler/Problem02.java

@@ -0,0 +1,43 @@
+package ProjectEuler;
+
+/**
+ * Each new term in the Fibonacci sequence is generated by adding the previous two terms.
+ * By starting with 1 and 2, the first 10 terms will be:
+ * <p>
+ * 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
+ * <p>
+ * By considering the terms in the Fibonacci sequence whose values do not exceed four million,
+ * find the sum of the even-valued terms.
+ * <p>
+ * Link: https://projecteuler.net/problem=2
+ */
+public class Problem02 {
+    public static void main(String[] args) {
+        int[][] testNumbers = {
+                {10, 10}, /* 2 + 8 == 10 */
+                {15, 10}, /* 2 + 8 == 10 */
+                {2, 2},
+                {1, 0},
+                {89, 44} /* 2 + 8 + 34 == 44 */
+        };
+
+        for (int[] ints : testNumbers) {
+            assert solution1(ints[0]) == ints[1];
+        }
+    }
+
+    private static int solution1(int n) {
+        int sum = 0;
+        int first = 1;
+        int second = 2;
+        while (second <= n) {
+            if (second % 2 == 0) {
+                sum += second;
+            }
+            int temp = first + second;
+            first = second;
+            second = temp;
+        }
+        return sum;
+    }
+}