Tune performance of p60

LivInTheLookingGlass · Aug 22, 2024 · 25f9669 · 25f9669
1 parent 081d5f4
commit 25f9669
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Showing 2 changed files with 14 additions and 17 deletions.
diff --git a/docs/src/javascript/p0060.rst b/docs/src/javascript/p0060.rst
@@ -5,8 +5,6 @@ View source code :source:`javascript/src/p0060.js`
 
 .. js:autofunction:: p0060
 
-.. js:autofunction:: isConcatPrime
-
 .. literalinclude:: ../../../javascript/src/p0060.js
    :language: javascript
    :linenos:

diff --git a/javascript/src/p0060.js b/javascript/src/p0060.js
@@ -19,12 +19,24 @@ exports.p0060 = function() {
     iterator.next(); // 5 is excluded because if a number ends with 5, it's divisible by 5
     const compat = new Map();
     for (const x of iterator) {
+        const strX = String(x);
         for (const y of cachedPrimes) {
-            if (isConcatPrime(x, y)) {
+            if (primes.isPrime(Number(`${strX}${y}`)) && primes.isPrime(Number(`${y}${strX}`))) {
                 for (const [a, b, c] of iters.combinations(compat.get(y) || new Set(), 3)) {
                     // remember these checks are commutative
                     if (compat.get(b).has(a) && compat.get(c).has(a) && compat.get(c).has(b)) {
-                        if (isConcatPrime(a, x) && isConcatPrime(b, x) && isConcatPrime(c, x)) {
+                        const strA = String(a);
+                        const strB = String(b);
+                        const strC = String(c);
+                        const concatenations = [
+                            Number(`${strA}${strX}`),
+                            Number(`${strX}${strA}`),
+                            Number(`${strB}${strX}`),
+                            Number(`${strX}${strB}`),
+                            Number(`${strC}${strX}`),
+                            Number(`${strX}${strC}`)
+                        ];
+                        if (concatenations.every(primes.isPrime)) {
                             return x + y + a + b + c;
                         }
                     }
@@ -44,18 +56,5 @@ exports.p0060 = function() {
     return -1;
 };
 
-/**
- * Tests if a pair of numbers generates a prime if concatenated in both orders.
- *
- * @param {number} x
- * @param {number} y
- * @return {number}
- */
-const isConcatPrime = function(x, y) {
-    const sx = x.toString();
-    const sy = y.toString();
-    return primes.isPrime(parseInt(sx + sy)) && primes.isPrime(parseInt(sy + sx));
-};
-
 const iters = require('./lib/iters.js');
 const primes = require('./lib/primes.js');