Data update

Task/Babbage-problem/AWK/babbage-problem-2.awk

@@ -0,0 +1,49 @@
+#!/usr/bin/awk -f
+# Quite efficient solution based on modulo arithmetic
+# needs 270 square/mod calculations (variable tally)
+# to calculate all solutions, and stop if none
+BEGIN {
+    q = 269696
+    if (ARGC > 1) q = ARGV[1]
+    # print q ":"
+    set[1] = 0
+    m = 1
+    while (m < q && length(set) > 0) {
+        new_set(set, m, q)
+        m *= 10
+    }
+    if (length(set) > 1) {
+        asort(set)
+        for (i in set) {
+            v = set[i]
+            printf("%6d^2 -- %12d\n", v, v*v)
+        }
+        print tally " square/mod calculations"
+    } else {
+        print "NO SOLUTION"
+    }
+}
+
+function new_set (old, m, q,        new, mm, qm, i, j, k, l) {
+    mm = 10 * m
+    qm = q % mm
+    for (i in old)
+        for (j = 0; j < 10*m; j += m) {
+            tally += 1
+            k = i + j
+            l = (k*k) % mm
+            if (l == qm)
+                new[k] = k
+        }
+    # new set in old
+    delete old
+    for (i in new)
+       old[i] = new[i]
+    # show(new)
+}
+
+function show(set) {
+    for (i in set)
+        printf("%d ", i)
+    print ""
+}