fix C++ tutorial, add solutions

Author: N-Coder

docs/build-tutorial-zip.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+
+rm tutorial.zip
+latexmk tutorial
+
+for f in {examples,exercises,tutorial}/*.py; do
+	jupytext -o "${f%.*}.ipynb" "$f"
+done
+
+zip -r tutorial.zip data examples/*.ipynb exercises/*.ipynb tutorial/*.ipynb build-ogdf.sh tutorial.pdf
+
+rm {examples,exercises,tutorial}/*.ipynb

docs/exercises/solution/1 tree layout.py

@@ -0,0 +1,37 @@
+# %%
+%matplotlib widget
+from ogdf_python import ogdf, cppinclude
+
+cppinclude("ogdf/basic/graph_generators/randomized.h")
+
+G = ogdf.Graph()
+ogdf.setSeed(1)
+ogdf.randomTree(G, 15)
+root = G.nodes[0]
+GA = ogdf.GraphAttributes(G, ogdf.GraphAttributes.all)
+
+G
+
+# %%
+post = ogdf.NodeArray[int](G, -1)
+depth = ogdf.NodeArray[int](G, -1)
+
+
+def postorder(n, count=0, level=0):
+    for adj in n.adjEntries:
+        if not adj.isSource():
+            continue
+        count = postorder(adj.twinNode(), count, level + 1)
+
+    depth[n] = level
+    post[n] = count
+    return count + 1
+
+
+postorder(root)
+
+# %%
+for n in G.nodes:
+    GA.y[n] = depth[n] * 50
+    GA.x[n] = post[n] * 50
+GA

docs/exercises/solution/2 topsort.py

@@ -0,0 +1,236 @@
+# %%
+# This cell generates a random graph for the topological sort to run on.
+
+%matplotlib widget
+from ogdf_python import ogdf, cppinclude
+import cppyy
+
+cppinclude("ogdf/basic/graph_generators/randomized.h")
+cppinclude("ogdf/layered/SugiyamaLayout.h")
+cppinclude("ogdf/basic/simple_graph_alg.h")
+
+G = ogdf.Graph()
+GA = ogdf.GraphAttributes(G, ogdf.GraphAttributes.all)
+GA.directed = True
+
+
+def make_graph():
+    ogdf.setSeed(1)
+    G.clear()
+    G2 = ogdf.Graph()
+    ogdf.randomPlanarTriconnectedGraph(G2, 10, 20)
+    G.insert(G2)
+    ogdf.randomPlanarTriconnectedGraph(G2, 5, 10)
+    G.insert(G2)
+    ogdf.makeAcyclicByReverse(G)
+
+    for e in G.edges:
+        GA.label[e] = str(e.index())
+    for n in G.nodes:
+        GA.label[n] = str(n.index())
+
+    SL = ogdf.SugiyamaLayout()
+    SL.call(GA)
+    GA.rotateLeft90()
+
+    G.delEdge(G.edges[4])  # add a second source
+
+
+make_graph()
+GA
+
+# %%
+good_order = [
+    G.nodes[7],
+    G.nodes[13],
+    G.nodes[12],
+    G.nodes[15],
+    G.nodes[5],
+    G.nodes[11],
+    G.nodes[14],
+    G.nodes[6],
+    G.nodes[10],
+    G.nodes[4],
+    G.nodes[8],
+    G.nodes[3],
+    G.nodes[2],
+    G.nodes[1],
+    G.nodes[9],
+    G.nodes[0],
+]
+bad_order = [
+    G.nodes[7],
+    G.nodes[13],
+    G.nodes[12],
+    G.nodes[15],
+    G.nodes[5],
+    G.nodes[11],
+    G.nodes[14],
+    G.nodes[6],
+    G.nodes[10],
+    G.nodes[3],
+    G.nodes[8],
+    G.nodes[4],
+    G.nodes[2],
+    G.nodes[1],
+    G.nodes[9],
+    G.nodes[0],
+]
+
+
+# %%
+def validate(order):
+    seen = set()
+    for n in order:
+        for adj in n.adjEntries:
+            if not adj.isSource():
+                continue
+            if not adj.twinNode() in seen:
+                print(adj)
+                return False
+        seen.add(n)
+    return True
+
+
+# %%
+validate(good_order)
+
+# %%
+validate(bad_order)
+
+# %%
+degree = ogdf.NodeArray[int](G, 0)  # degree after node deletion
+for n in G.nodes:
+    degree[n] = n.outdeg()
+    if degree[n] == 0:
+        GA.fillColor[n] = ogdf.Color("#FCC")
+sinks = [n for n in G.nodes if degree[n] == 0]  # sink nodes
+
+order = []  # order of nodes
+index = ogdf.NodeArray[int](G, -1)  # position in order
+
+# %%
+import random
+
+
+def step():
+    n = sinks.pop(random.randrange(len(sinks)))
+    index[n] = i = len(order)
+    order.append(n)
+
+    GA.label[n] = f"{i}"
+    GA.strokeColor[n] = ogdf.Color("#666")
+    GA.fillColor[n] = ogdf.Color("#CCC")
+
+    # (virtually) remove all edges to n
+    for adj in n.adjEntries:
+        GA.strokeColor[adj.theEdge()] = ogdf.Color("#CCC")
+
+        if adj.isSource():
+            continue
+        # else n is the target of the "removed" edge
+        # decrement the outdegree of the source of the edge
+        degree[adj.twinNode()] -= 1
+        if degree[adj.twinNode()] == 0:
+            sinks.append(adj.twinNode())
+            GA.fillColor[adj.twinNode()] = ogdf.Color("#FCC")
+
+
+# %%
+def dump():
+    print("Order:", *order)
+    print("Sinks:", *sinks)
+    for n in sinks:
+        GA.fillColor[n] = ogdf.Color("#FCC")
+    return GA
+
+
+dump()
+
+# %%
+step()
+dump()
+
+# %%
+step()
+dump()
+
+# %%
+step()
+dump()
+
+# %%
+import ipywidgets
+from ogdf_python.matplotlib import MatplotlibGraph
+
+w = MatplotlibGraph(GA)
+w_order = ipywidgets.Label()
+w_sinks = ipywidgets.Label()
+b_step = ipywidgets.Button(description="Step")
+b_reset = ipywidgets.Button(description="Reset")
+
+
+def update():
+    w_order.value = "Order: " + ", ".join(str(n.index()) for n in order)
+    w_sinks.value = "Sinks: " + ", ".join(str(n.index()) for n in sinks)
+    b_step.disabled = not sinks
+
+
+def b_step_click(*args):
+    step()
+    update()
+    w.update_node(order[-1])
+    for adj in order[-1].adjEntries:
+        w.update_edge(adj.theEdge())
+    for s in sinks:
+        w.update_node(s)
+
+
+b_step.on_click(b_step_click)
+
+
+def b_reset_click(*args):
+    make_graph()
+    order.clear()
+    sinks.clear()
+    sinks.extend(n for n in G.nodes if n.outdeg() == 0)
+    for n in G.nodes:
+        degree[n] = n.outdeg()
+        if degree[n] == 0:
+            GA.fillColor[n] = ogdf.Color("#FCC")
+    update()
+    w.update_all()
+
+
+b_reset.on_click(b_reset_click)
+
+update()
+ipywidgets.VBox(
+    [ipywidgets.HBox([b_step, b_reset]), w_order, w_sinks, w.ax.figure.canvas]
+)
+
+# %%
+N = list(G.nodes)
+print("[", ", ".join(f"G.nodes[{N.index(n)}]" for n in order), "]")
+
+# %%
+# allow changing the displayed node label
+d_label = ipywidgets.Dropdown(
+    options=["Index", "Degree"],
+    value="Index",
+    description="Node label:",
+    disabled=False,
+)
+
+
+def label_changed(change):
+    for n in G.nodes:
+        if index[n] == -1:
+            GA.label[n] = (
+                str(n.index()) if change["new"] == "Index" else f"d{degree[n]}"
+            )
+    w.update_all()
+
+
+d_label.observe(label_changed, names="value")
+d_label