week 2 challenge

fall23/Week2/Week2.java

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+package fall23.Week2;
+
+/**
+ * Sum of Multiples of 3 or 5.
+ *
+ * In this week's club challenge, find the sum of each multiple of either 3 or 5, with the condition that the multiple is less than 1000.
+ *      eg. For multiples of 3 or 5 below 10, the answer would be the 3 + 5 + 6 + 9 = 23.
+ *
+ * Credit: Project Euler Problem 1.
+ */
+public class Week2 {
+
+    /**
+     * HINT: Solution 1 uses 1000 iterations in 1 loop. 
+     */
+    public static int problem1() {
+        int sum = 0;
+
+        for(int i = 0; i < 1000; i++) {
+            if(i % 5 == 0 || i % 3 == 0) sum += i;
+        }
+
+        return sum;
+    }
+
+    /**
+     * BONUS CHALLENGE: Find a more efficient solution for problem 1 (ie. a solution that uses less than 1000 iterations).
+     */
+    public static int problem2() {
+        int sum = 0;
+        for(int i = 5; i < 1000; i+=5)
+            sum += i;
+
+        for(int i = 3; i < 1000; i+=3) 
+            if(i % 5 != 0) sum += i;
+
+        return sum;
+    }
+
+    /**
+     * Test driver should not be edited!
+     */
+    public static void main(String[] args) {
+        int sum1 = problem1();
+        int sum2 = problem2();
+
+        System.out.println(sum1 == 233168 ? "Problem 1 is correct!" : "Problem 1 (" + sum1 + ") is not correct...");
+        System.out.println(sum2 == 233168 ? "Problem 2 is correct!" : "Problem 2 (" + sum2 + ") is not correct...");
+    }
+}