Module:Utils: Difference between revisions

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@@ Line 154: / Line 154: @@
 	if x < 0 then return -1 end
 	return 0
+end
+-- returns the next Young diagram of the same size or nil; cannot be used with {{#invoke:}}
+-- modifies the input table
+function p.next_young_diagram(d)
+	if #d == 0 then
+		return nil
+	end
+	local i_from = nil
+	local size = 0
+	for i = #d, 1, -1 do
+		if d[i] > 1 then
+			i_from = i
+			break
+		end
+		size = size + d[i]
+	end
+	if i_from == nil then
+		return nil
+	end
+	d[i_from] = d[i_from] - 1
+	size = size + 1
+	-- repacking the tail
+	local max_d = d[i_from]
+	for i = i_from + 1, #d + 1 do
+		if size >= max_d then
+			d[i] = max_d
+			size = size - max_d
+		elseif size > 0 then
+			d[i] = size
+			size = 0
+		else
+			d[i] = nil
+		end
+	end
+	return d
 end
 return p