p2-p4

src/main/java/p050/P002SumOfEvenFibonacci.java

@@ -0,0 +1,30 @@
+package p050;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class P002SumOfEvenFibonacci {
+
+    private static final int LIMIT = 4000000;
+
+    private static List<Integer> generateFibonacci(int limit) {
+        List<Integer> f = new ArrayList<>();
+        f.add(1);
+        f.add(1);
+        int index = 1;
+        while (f.get(index) <= limit) {
+            f.add(f.get(index) + f.get(index - 1));
+            index++;
+        }
+        return f;
+    }
+
+
+    public static void main(String[] args) {
+        int sum = generateFibonacci(LIMIT)
+            .stream()
+            .filter(it -> it % 2 == 0)
+            .reduce(0, (a, b) -> a + b);
+        System.out.println("sum even fibonacci  = " + sum);
+    }
+}

src/main/java/p050/P003MaxPrimeFactor.java

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+package p050;
+
+public class P003MaxPrimeFactor {
+
+    private static final long LIMIT = 600851475143L;
+
+    public static void main(String[] args) {
+        int factor = 2;
+        int maxPrimeFactor = 1;
+
+        long number = LIMIT;
+        while (number > 1 || number > factor) {
+            if (number % factor == 0) {
+                maxPrimeFactor = factor;
+                while (number % factor == 0 && number > 1) {
+                    number /= factor;
+                }
+            }
+            factor++;
+        }
+
+        System.out.println("max prime factor " + maxPrimeFactor);
+    }
+}

src/main/java/p050/P004LargestPalindrom.java

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+package p050;
+
+public class P004LargestPalindrom {
+
+    private static boolean palindrom(int n) {
+        String a = String.valueOf(n);
+
+        StringBuilder sb = new StringBuilder();
+        for (int i = a.length() - 1; i >= 0; i--) {
+            sb.append(a.charAt(i));
+        }
+
+        return a.equals(sb.toString());
+    }
+
+    public static void main(String[] args) {
+
+        int maxI = -1;
+        int maxJ = -1;
+        int max = -1;
+        for (int i = 999; i >= 100; i--) {
+            for (int j = i; j >= 100; j--) {
+                int p = i * j;
+                if (palindrom(p)) {
+                    if (max < p) {
+                        max = p;
+                        maxI = i;
+                        maxJ = j;
+                    }
+
+                    // no need to iterate j further
+                    break;
+                }
+            }
+        }
+
+        System.out.println("max palindrome = " + max + " (" + maxI + " * " + maxJ + ")");
+    }
+}

src/main/java/p050/P005SmallestMultiple.java

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+package p050;
+
+public class P005SmallestMultiple {
+}