Merge pull request #60 from wakidurrahman/feat/primality-test

Number Algorithms

Author: wakidurrahman

src/problems/isPrime-01.ts

@@ -0,0 +1,64 @@
+/**
+ *
+ * Number Algorithms
+ * One of the most discussed algorithms involving numbers is for testing whether a number is a prime number..
+ * @returns
+ */
+// Algorithm 01:  A primality test can be done by iterating from 2 to n, checking whether modulus division (remainder) is equal to zero.
+// 2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97
+function isPrimeOne(n: number) {
+  if (n <= 1) {
+    return false;
+  }
+
+  // check from 2 to n - 1;
+  for (let i = 2; i < n; i++) {
+    if (n % i == 0) {
+      return false;
+    }
+  }
+
+  return true;
+} // Time complexity: O(n)
+
+function isPrimeTwo(n: number) {
+  if (n <= 1) return false;
+  if (n <= 3) return true;
+
+  // This is checked so that we can skip
+  // Middle five numbers in below loop
+
+  if (n % 2 == 0 || n % 3 == 0) return false;
+
+  for (let i = 5; i * i <= n; i = i + 6) {
+    if (n % i == 0 || n % (i + 2) == 0) return false;
+  }
+  return true;
+} // O(sqrt(n))
+
+function primeFactors(n: number) {
+  // Print the number of 2s that divide n
+  while (n % 2 == 0) {
+    console.log(2);
+    n = n / 2;
+  }
+
+  // n must be odd at this point. So we can skip one element
+  // note i = i + 2;
+  for (let i = 3; i * i <= n; i = i + 2) {
+    // While i divides n, print i and divide n
+    while (n % i == 0) {
+      console.log(i);
+      n = n / i;
+    }
+  }
+  // This condition is to handle the case when n is a prime number greater than 2
+  if (n > 2) {
+    console.log(n);
+  }
+} // O(sqrt(n))
+
+// Random Number Generator
+Math.random() * 100; // floats between 0 and 100;
+Math.random() * 25 + 5; // floats between 5 and 30
+Math.random() * 10 - 100; // floats between -100 and -90