Data commit

Task/Partition-function-P/Wren/partition-function-p.wren

@@ -0,0 +1,36 @@
+import "/big" for BigInt
+
+var p = []
+var pd = []
+
+var partDiffDiff = Fn.new { |n| (n&1 == 1) ? (n + 1)/2 : n + 1 }
+
+var partDiff = Fn.new { |n|
+    if (n < 2) return 1
+    pd[n] = pd[n-1] + partDiffDiff.call(n-1)
+    return pd[n]
+}
+
+var partitionsP = Fn.new { |n|
+    if (n < 2) return
+    var psum = BigInt.zero
+    for (i in 1..n) {
+        var pdi = partDiff.call(i)
+        if (pdi > n) break
+        var sign = (i-1)%4 < 2 ? 1 : -1
+        psum = psum + p[n-pdi] * sign
+    }
+    p[n] = psum
+}
+
+var start = System.clock
+var N = 6666
+p = List.filled(N+1, null)
+pd = List.filled(N+1, 0)
+p[0] = BigInt.one
+p[1] = BigInt.one
+pd[0] = 1
+pd[1] = 1
+for (n in 2..N) partitionsP.call(n)
+System.print("p[%(N)] = %(p[N])")
+System.print("Took %(System.clock - start) seconds")