Created Problem07 in Project Euler

Author: realDuYuanChao

ProjectEuler/Problem07.java

@@ -0,0 +1,59 @@
+package ProjectEuler;
+
+/**
+ * By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13.
+ * <p>
+ * What is the 10 001st prime number?
+ * <p>
+ * link: https://projecteuler.net/problem=7
+ */
+public class Problem07 {
+    public static void main(String[] args) {
+        int[][] testNumbers = {
+                {1, 2},
+                {2, 3},
+                {3, 5},
+                {4, 7},
+                {5, 11},
+                {6, 13},
+                {20, 71},
+                {50, 229},
+                {100, 541}
+        };
+        for (int[] number : testNumbers) {
+            assert solution1(number[0]) == number[1];
+        }
+    }
+
+    /***
+     * Checks if a number is prime or not
+     * @param number the number
+     * @return {@code true} if {@code number} is prime
+     */
+    private static boolean isPrime(int number) {
+        if (number == 2) {
+            return true;
+        }
+        if (number < 2 || number % 2 == 0) {
+            return false;
+        }
+        for (int i = 3, limit = (int) Math.sqrt(number); i <= limit; i += 2) {
+            if (number % i == 0) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    private static int solution1(int n) {
+        int count = 0;
+        int number = 1;
+
+        while (count != n) {
+            if (isPrime(++number)) {
+                count++;
+            }
+        }
+        return number;
+    }
+}