Solutions for challenge #147

2 files changed, 138 insertions, 0 deletions

diff --git a/challenge-147/roger-bell-west/javascript/ch-1.js b/challenge-147/roger-bell-west/javascript/ch-1.js
new file mode 100755
index 0000000000..3ad09c3efd
--- /dev/null
+++ b/challenge-147/roger-bell-west/javascript/ch-1.js
@@ -0,0 +1,97 @@
+#! /usr/bin/node
+
+// by Frank Tan
+// https://stackoverflow.com/questions/38400594/javascript-deep-comparison
+function deepEqual(a,b)
+{
+    if( (typeof a == 'object' && a != null) &&
+        (typeof b == 'object' && b != null) )
+    {
+        var count = [0,0];
+        for( var key in a) count[0]++;
+        for( var key in b) count[1]++;
+        if( count[0]-count[1] != 0) {return false;}
+        for( var key in a)
+        {
+            if(!(key in b) || !deepEqual(a[key],b[key])) {return false;}
+        }
+        for( var key in b)
+        {
+            if(!(key in a) || !deepEqual(b[key],a[key])) {return false;}
+        }
+        return true;
+    }
+    else
+    {
+        return a === b;
+    }
+}
+
+function genprimes(mx) {
+    let primesh=new Set([2,3]);
+    for (let i = 6; i <= mx+1; i += 6) {
+        for (let j = i-1; j <= i+1; j += 2) {
+            if (j <= mx) {
+                primesh.add(j);
+            }
+        }
+    }
+    let q=[2,3,5,7];
+    let p=q.shift();
+    let mr=Math.floor(Math.sqrt(mx));
+    while (p <= mr) {
+        if (primesh.has(p)) {
+            let i=p*p
+            for (let i=p*p; i <= mx; i += p) {
+                primesh.delete(i);
+            }
+        }
+        if (q.length < 2) {
+            q.push(q[q.length-1]+4);
+            q.push(q[q.length-1]+2);
+        }
+        p=q.shift();
+    }
+    let primes=[...primesh];
+    primes.sort(function(a,b) {
+        return a-b;
+    });
+    return primes;
+}
+
+function tos(n) {
+    return n.toString();
+}
+
+function ltruncprimes(count) {
+    let out=[];
+    let lt=0;
+    let p=genprimes(500).map(tos);
+    let pp=new Set(p);
+    for (let pc of p) {
+        let l=pc.length;
+        let c=true;
+        for (let i=1;i<l;i++) {
+            if (!pp.has(pc.slice(i))) {
+                c=false;
+                break;
+            }
+        }
+        if (c) {
+            out.push(parseInt(pc));
+            lt++;
+            if (lt >= count) {
+                break;
+            }
+        }
+    }
+    return out;
+}
+
+if (deepEqual(ltruncprimes(20),[2, 3, 5, 7, 13, 17, 23, 37, 43, 47, 53, 67, 73, 83, 97, 113, 137, 167, 173, 197])) {
+    process.stdout.write("Pass");
+} else {
+    process.stdout.write("FAIL");
+}
+process.stdout.write("\n");
+
diff --git a/challenge-147/roger-bell-west/javascript/ch-2.js b/challenge-147/roger-bell-west/javascript/ch-2.js
new file mode 100755
index 0000000000..8d55a5edde
--- /dev/null
+++ b/challenge-147/roger-bell-west/javascript/ch-2.js
@@ -0,0 +1,41 @@
+#! /usr/bin/node
+
+function pentagon(n) {
+    return Math.floor(n*(3*n-1)/2);
+}
+
+function pentpair() {
+    let fpent=[0];
+    let rpent=new Map();
+    let mx=0;
+    let a=1;
+    while (true) {
+        while (mx < a) {
+            mx++;
+            fpent.push(pentagon(mx));
+            rpent.set(fpent[mx],mx);
+        }
+        for (b = 1; b < a; b++) {
+            let d=fpent[a]-fpent[b];
+            if (d < fpent[b]) {
+                break;
+            }
+            if (rpent.has(d)) {
+                let s=fpent[a]+fpent[b];
+                while (s > fpent[mx]) {
+                    mx++;
+                    fpent.push(pentagon(mx));
+                    rpent.set(fpent[mx],mx);
+                }
+                if (rpent.has(s)) {
+                    console.log("P(%d) + P(%d) = %d + %d = %d = P(%d)",a,b,fpent[a],fpent[b],s,rpent.get(s));
+                    console.log("P(%d) - P(%d) = %d - %d = %d = P(%d)",a,b,fpent[a],fpent[b],d,rpent.get(d));
+                    throw '';
+                }
+            }
+        }
+        a++;
+    }
+}
+
+pentpair();