Number Algorithms

Author: Wakidur Rahaman

src/problems/isPrime-01.ts

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+/**
+ *
+ * Number Algorithms
+ * One of the most discussed algorithms involving numbers is for testing whether a number is a prime number..
+ * @returns
+ */
+// A primality test can be done by iterating from 2 to n, checking whether modulus division (remainder) is equal to zero.
+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))