Week 147: bc solutions

2 files changed, 98 insertions, 0 deletions

diff --git a/challenge-147/abigail/bc/ch-1.bc b/challenge-147/abigail/bc/ch-1.bc
new file mode 100644
index 0000000000..52d5cdb0f0
--- /dev/null
+++ b/challenge-147/abigail/bc/ch-1.bc
@@ -0,0 +1,57 @@
+#!/usr/bin/bc
+
+#
+# See https://theweeklychallenge.org/blog/perl-weekly-challenge-147
+#
+
+#
+# Run as: bc ch-1.bc
+#
+
+define is_prime (p) {
+    auto d
+    if (p == 2) {return 1}
+    if (p % 2 == 0) {return 0}
+    for (d = 3; d * d <= p; d += 2) {
+        if (p % d == 0) {return 0}
+    }
+    return 1
+}
+
+todo [1] = 2
+todo [2] = 3
+todo [3] = 5
+todo [4] = 7
+high = 4
+
+for (i = 1; i <= high; i ++) {
+    print todo [i], " "
+}
+
+count = 20 - high
+
+pow = 10
+while (count > 0) {
+    new_high = 0
+    for (d = 1; d <= 9 && count > 0; d ++) {
+        for (i = 1; i <= high && count > 0; i ++) {
+            candidate = d * pow + todo [i]
+            if (is_prime (candidate)) {
+                print candidate, " "
+                new_high = new_high + 1
+                count = count - 1
+                next [new_high] = candidate
+            }
+        }
+    }
+    for (j = 1; j <= new_high; j ++) {
+        todo [j] = next [j]
+    }
+    high = new_high
+    pow = pow * 10
+}
+
+"
+"
+
+halt
diff --git a/challenge-147/abigail/bc/ch-2.bc b/challenge-147/abigail/bc/ch-2.bc
new file mode 100644
index 0000000000..6aee8ec9b4
--- /dev/null
+++ b/challenge-147/abigail/bc/ch-2.bc
@@ -0,0 +1,41 @@
+#!/usr/bin/bc
+
+#
+# See https://theweeklychallenge.org/blog/perl-weekly-challenge-147
+#
+
+#
+# Run as: bc ch-2.bc
+#
+
+define is_pentagonal (p) {
+    auto l, h, m
+    l = l
+    h = high
+    while (l <= h) {
+        m = (l + h) / 2
+        if (pentagon [m] == p) {return 1}
+        if (pentagon [m] <  p) {l = m + 1} else {h = m - 1}
+    }
+    return 0
+}
+
+while (!done) {
+    p = p + n + n + n + 1
+    n = n + 1
+    high = high + 1
+
+    pentagon [high] = p
+
+    for (i = 1; i <= high && pentagon [i] + pentagon [i] < p && !done; i ++) {
+        seen = pentagon [i]
+        
+        if (is_pentagonal (p - seen) && is_pentagonal (p - seen - seen)) {
+            print seen, " "
+            p - seen
+            done = 1
+        }
+    }
+}
+
+halt