shuffleAllBut for graphs

doc/graph.md

@@ -74,3 +74,12 @@ All options are unset by default. If the generator contradicts some option (like
     * relabel vertices in random order;
     * shuffle edges;
     * randomly swap egdes' endpoints (for undirected graphs only).
+
+#### Graph& shuffleAllBut(const Array& except)
+#### Graph shuffledAllBut(const Array& except)
+* Same as *shuffle*, but vertices from *except* do not change their numbers.
+    * Possible usecase: we may generate a graph where *s-t* path is supposed to be found. Then shuffle the graph in such a way that path endpoints are still *1* and *n*:
+```cpp
+g = Graph::random(n, m)...;
+g.shuffleAllBut({0, n-1});
+```

doc/tree.md

@@ -47,6 +47,15 @@ Note that all generators return trees with sorted edges to make tests more human
     * shuffle edges;
     * randomly swap egdes' endpoints.
 
+#### Tree& shuffleAllBut(const Array& except)
+#### Tree shuffledAllBut(const Array& except)
+* Same as *shuffle*, but vertices from *except* do not change their numbers.
+    * Possible usecase: we may generate a rooted tree and shuffle it in such a way that root still has number *1*.
+```cpp
+t = Tree::randomPrim(n, 1000);
+t.shuffleAllBut({0});
+```
+
 #### Array parents(int root) const
 * Returns: array of size *n*, where *i*-th element is a parent of vertex *i* if the tree is rooted at *root*. Parent of *root* is *-1*.
 

generic_graph.h

@@ -65,6 +65,8 @@ class GenericGraph {
     static WeightArray prepareWeightArray(WeightArray a, int requiredSize);
 
     void doShuffle();
+    void doShuffleAllBut(const Array& except);
+    void doShuffleEdges();
 
     void extend(size_t size);
 

graph.h

@@ -33,6 +33,8 @@ class Graph : public ReprProxy<Graph>, public GenericGraph {
 
     Graph& shuffle();
     Graph shuffled() const;
+    Graph& shuffleAllBut(const Array& except);
+    Graph shuffledAllBut(const Array& except) const;
 
     static BuilderProxy random(int n, int m);
     static BuilderProxy complete(int n);
@@ -57,6 +59,16 @@ inline Graph Graph::shuffled() const {
     return g.shuffle();
 }
 
+inline Graph& Graph::shuffleAllBut(const Array& except) {
+    doShuffleAllBut(except);
+    return *this;
+}
+
+inline Graph Graph::shuffledAllBut(const Array& except) const {
+    Graph g(*this);
+    return g.shuffleAllBut(except);
+}
+
 JNGEN_DECLARE_SIMPLE_PRINTER(Graph, 2) {
     t.doPrintEdges(out, mod);
 }

impl/generic_graph_inl.h

@@ -99,6 +99,29 @@ void GenericGraph::doShuffle() {
     vertexLabel_.shuffle();
     vertexByLabel_ = vertexLabel_.inverse();
 
+    doShuffleEdges();
+}
+
+void GenericGraph::doShuffleAllBut(const Array& except) {
+    Array index = except.sorted();
+    Array needed = Array::id(n());
+    needed.erase(std::set_difference(
+                needed.begin(), needed.end(),
+                index.begin(), index.end(),
+                needed.begin()), needed.end());
+    Array neededShuffled = needed.shuffled();
+    Array perm = Array::id(n());
+    for (size_t i = 0; i < needed.size(); ++i) {
+        perm[needed[i]] = neededShuffled[i];
+    }
+
+    vertexLabel_ = vertexLabel_.subseq(perm);
+    vertexByLabel_ = vertexLabel_.inverse();
+
+    doShuffleEdges();
+}
+
+void GenericGraph::doShuffleEdges() {
     if (!directed_) {
         for (auto& edge: edges_) {
             if (rnd.next(2)) {

impl/tree_inl.h

@@ -63,6 +63,16 @@ Tree Tree::shuffled() const {
     return t.shuffle();
 }
 
+inline Tree& Tree::shuffleAllBut(const Array& except) {
+    doShuffleAllBut(except);
+    return *this;
+}
+
+inline Tree Tree::shuffledAllBut(const Array& except) const {
+    Tree g(*this);
+    return g.shuffleAllBut(except);
+}
+
 Tree Tree::link(int vInThis, const Tree& other, int vInOther) {
     ensure(vInThis < n(), "Cannot link a nonexistent vertex");
     ensure(vInOther < other.n(), "Cannot link to a nonexistent vertex");

jngen.h

@@ -5492,6 +5492,8 @@ class GenericGraph {
     static WeightArray prepareWeightArray(WeightArray a, int requiredSize);
 
     void doShuffle();
+    void doShuffleAllBut(const Array& except);
+    void doShuffleEdges();
 
     void extend(size_t size);
 
@@ -5643,6 +5645,29 @@ void GenericGraph::doShuffle() {
     vertexLabel_.shuffle();
     vertexByLabel_ = vertexLabel_.inverse();
 
+    doShuffleEdges();
+}
+
+void GenericGraph::doShuffleAllBut(const Array& except) {
+    Array index = except.sorted();
+    Array needed = Array::id(n());
+    needed.erase(std::set_difference(
+                needed.begin(), needed.end(),
+                index.begin(), index.end(),
+                needed.begin()), needed.end());
+    Array neededShuffled = needed.shuffled();
+    Array perm = Array::id(n());
+    for (size_t i = 0; i < needed.size(); ++i) {
+        perm[needed[i]] = neededShuffled[i];
+    }
+
+    vertexLabel_ = vertexLabel_.subseq(perm);
+    vertexByLabel_ = vertexLabel_.inverse();
+
+    doShuffleEdges();
+}
+
+void GenericGraph::doShuffleEdges() {
     if (!directed_) {
         for (auto& edge: edges_) {
             if (rnd.next(2)) {
@@ -5864,6 +5889,8 @@ class Tree : public ReprProxy<Tree>, public GenericGraph {
 
     Tree& shuffle();
     Tree shuffled() const;
+    Tree& shuffleAllBut(const Array& except);
+    Tree shuffledAllBut(const Array& except) const;
 
     Tree link(int vInThis, const Tree& other, int vInOther);
     Tree glue(int vInThis, const Tree& other, int vInOther);
@@ -5969,6 +5996,16 @@ Tree Tree::shuffled() const {
     return t.shuffle();
 }
 
+inline Tree& Tree::shuffleAllBut(const Array& except) {
+    doShuffleAllBut(except);
+    return *this;
+}
+
+inline Tree Tree::shuffledAllBut(const Array& except) const {
+    Tree g(*this);
+    return g.shuffleAllBut(except);
+}
+
 Tree Tree::link(int vInThis, const Tree& other, int vInOther) {
     ensure(vInThis < n(), "Cannot link a nonexistent vertex");
     ensure(vInOther < other.n(), "Cannot link to a nonexistent vertex");
@@ -6205,6 +6242,8 @@ class Graph : public ReprProxy<Graph>, public GenericGraph {
 
     Graph& shuffle();
     Graph shuffled() const;
+    Graph& shuffleAllBut(const Array& except);
+    Graph shuffledAllBut(const Array& except) const;
 
     static BuilderProxy random(int n, int m);
     static BuilderProxy complete(int n);
@@ -6229,6 +6268,16 @@ inline Graph Graph::shuffled() const {
     return g.shuffle();
 }
 
+inline Graph& Graph::shuffleAllBut(const Array& except) {
+    doShuffleAllBut(except);
+    return *this;
+}
+
+inline Graph Graph::shuffledAllBut(const Array& except) const {
+    Graph g(*this);
+    return g.shuffleAllBut(except);
+}
+
 JNGEN_DECLARE_SIMPLE_PRINTER(Graph, 2) {
     t.doPrintEdges(out, mod);
 }

tree.h

@@ -26,6 +26,8 @@ class Tree : public ReprProxy<Tree>, public GenericGraph {
 
     Tree& shuffle();
     Tree shuffled() const;
+    Tree& shuffleAllBut(const Array& except);
+    Tree shuffledAllBut(const Array& except) const;
 
     Tree link(int vInThis, const Tree& other, int vInOther);
     Tree glue(int vInThis, const Tree& other, int vInOther);