refa: solve overseparation of logic

Author: JCPedroza

src/project-euler/009-special-pythagorean-triplet/README.md

@@ -23,11 +23,3 @@ The function signature is
 ```typescript
 function specialPythagoreanTriplet(targetSum: number): number
 ```
-
-## Resources
-
-- [Project Euler Problem 009][1]
-- [Project Euler Problem 009 at freeCodeCamp][2]
-
-[1]: https://projecteuler.net/problem=9
-[2]: https://www.freecodecamp.org/learn/coding-interview-prep/project-euler/problem-9-special-pythagorean-triplet

src/project-euler/009-special-pythagorean-triplet/special-pythagorean-triplet-naive.js

@@ -1,49 +1,34 @@
-// Check if triplet holds invariant a² + b² = c²
-const isSquareValid = ([a, b, c]) => a ** 2 + b ** 2 === c ** 2
-
-// Check if triplet holds invariant a + b + c = targetSum
-const isSumValid = ([a, b, c], targetSum) => a + b + c === targetSum
-
-// Check if triplet holds invariant a < b < c
-const isRelValid = ([a, b, c]) => a < b && b < c
-
-// Throws an error if triplet doesn't hold sum or relation invariants
-const validateTriplet = (triplet, targetSum) => {
-  if (!isSumValid(triplet, targetSum) || !isRelValid(triplet)) {
-    throw new Error(`Invalid triplet ${triplet}`)
-  }
-}
-
-// Computes next triplet iteration, while holding sum and relation invariants
-const increaseTriplet = (triplet, targetSum) => {
-  const [a, b, c] = triplet
-
-  validateTriplet(triplet, targetSum)
-
-  if (b + 2 < c) {
-    triplet[1] = b + 1
-    triplet[2] = c - 1
-  } else {
-    triplet[0] = a + 1
-    triplet[1] = a + 2
-    triplet[2] = targetSum - triplet[0] - triplet[1]
-  }
-}
-
 /**
  * Compute the product of the pythagorean triplet where a + b + c = targetSum.
+ *
  * @param {number} targetSum Sum of triplet must equal this value.
  * @throws {Error} If an invalid triplet is ever reached.
  * @returns {number} Product of triplet found, where a + b + c = targetSum.
  */
 const specialPythagoreanTriplet = (targetSum) => {
-  const triplet = [1, 2, targetSum - 3]
-
-  while (!isSquareValid(triplet)) {
-    increaseTriplet(triplet, targetSum)
+  const tri = [1, 2, targetSum - 3]
+
+  while (!(tri[0] ** 2 + tri[1] ** 2 === tri[2] ** 2)) {
+    const [a, b, c] = tri
+
+    const isSumTarget = a + b + c === targetSum
+    const isAscending = a < b && b < c
+
+    if (!isSumTarget || !isAscending) {
+      throw new Error(`Invalid triplet ${[a, b, c]}`)
+    }
+
+    if (b + 2 < c) {
+      tri[1] = b + 1
+      tri[2] = c - 1
+    } else {
+      tri[0] = a + 1
+      tri[1] = a + 2
+      tri[2] = targetSum - tri[0] - tri[1]
+    }
   }
 
-  return triplet.reduce((acc, num) => acc * num)
+  return tri[0] * tri[1] * tri[2]
 }
 
 module.exports = {