projEuler12.ts

inputs/passing/projEuler12.ts

@@ -0,0 +1,85 @@
+declare const Debug: {
+  log: (...args: unknown[]) => undefined;
+};
+
+export default function main() {
+  let triNum = 0;
+
+  for (let i = 1; ; i++) {
+    triNum += i;
+    const factorCount = countFactors(triNum);
+
+    if (factorCount > 500) {
+      return triNum;
+    }
+  }
+}
+
+function countFactors(n: number): number {
+  const primeFactors = factorize(n);
+
+  let count = 1;
+  let power = 0;
+  let prevFactor = 0;
+
+  for (let i = 0; i <= primeFactors.length; i++) {
+    const factor = primeFactors[i];
+
+    if (factor !== prevFactor) {
+      count *= power + 1;
+      power = 1;
+      prevFactor = factor;
+    } else {
+      power++;
+    }
+  }
+
+  return count;
+}
+
+function factorize(n: number): number[] {
+  let factors: number[] = [];
+  let p = 2;
+
+  while (true) {
+    while (n % p === 0) {
+      factors.push(p);
+      n /= p;
+    }
+
+    if (n === 1) {
+      return factors;
+    }
+
+    p = nextOddPrime(p);
+
+    if (p * p > n) {
+      factors.push(n);
+      return factors;
+    }
+  }
+}
+
+function nextOddPrime(n: number): number {
+  n += 1 + (n % 2); // Next odd number
+
+  while (!isOddPrime(n)) {
+    n += 2;
+  }
+
+  return n;
+}
+
+function isOddPrime(n: number): boolean {
+  let i = 3;
+
+  while (i * i <= n) {
+    if (n % i === 0) {
+      return false;
+    }
+
+    i += 2;
+  }
+
+  return true;
+}