Problem 30

src/main/java/net/projecteuler/problems/problems026to050/Problem030.java

@@ -0,0 +1,35 @@
+package net.projecteuler.problems.problems026to050;
+
+import java.util.stream.IntStream;
+
+public class Problem030 {
+
+  private static final int POWER = 5;
+
+  private static int sumOfFifthPowers(int number) {
+    return Integer.toString(number).chars()
+      .map(Character::getNumericValue)
+      .map(i -> (int) Math.pow(i, 5))
+      .sum();
+  }
+
+  private static int getBound(int power, int base) {
+    var number = power * (int) Math.pow(base, 5);
+    var maxLength = Integer.toString(number).length();
+
+    while (Integer.toString(number).length() <= maxLength) {
+      power++;
+      number = power * (int) Math.pow(base, 5);
+    }
+    return number;
+  }
+
+  public int solve() {
+    var start = getBound(POWER, 1);
+    var end = getBound(POWER, 9);
+
+    return IntStream.rangeClosed(start, end)
+      .filter(number -> number == sumOfFifthPowers(number))
+      .sum();
+  }
+}

src/test/java/net/projecteuler/problems/problems026to050/Problem030Test.java

@@ -0,0 +1,13 @@
+package net.projecteuler.problems.problems026to050;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class Problem030Test {
+
+  @Test
+  void solve() {
+    assertEquals(443839, new Problem030().solve());
+  }
+}