Merge pull request #472 from victorialo/eulerProblem7

Euler Problem 7

Project-Euler/Problem7.js

@@ -0,0 +1,31 @@
+// https://projecteuler.net/problem=7
+// My approach does not use the Sieve of Eratosthenes but that is another common way to approach this problem. Sieve of Atkin is another possibility as well.
+
+const num = 10001
+const primes = [2, 3, 5, 7, 11, 13] // given list of primes you start with
+
+const calculatePrime = (num) => {
+  // Calculate each next prime by checking each number to see what it's divisible by
+  let count = primes.length // count number of primes calculated
+  let current = primes[count - 1] + 1 // current number being assessed if prime
+  while (count < num) { // repeat while we haven't reached goal number of primes
+    // go through each prime and see if divisible by the previous primes
+    let prime = false
+    primes.some((n, i) => {
+      if (current % n === 0) {
+        return true
+      }
+      if (i === count - 1) {
+        prime = true
+      }
+    })
+    if (prime) { // if prime, add to prime list and increment count
+      primes.push(current)
+      count += 1
+    }
+    current += 1
+  }
+  return primes[num - 1]
+}
+
+console.log(calculatePrime(num))