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fixed bugs in implementation of "find k shortest paths" algorithm

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This commit is contained in:
nik
2014-02-14 12:07:58 +04:00
parent bbe5c6c2a4
commit 864bf0f6da
2 changed files with 40 additions and 23 deletions
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platform/platform-impl/src/com/intellij/util/graph/impl/KShortestPathsFinder.java
+18 -23
View File
@@ -102,14 +102,12 @@ public class KShortestPathsFinder<Node> {
for (int j = 1; j < heapNodes.size(); j++) {
HeapNode<Node> heapNode = heapNodes.get(j);
HeapNode<Node> parent = heapNodes.get((j+1)/2 - 1);
heapNode.myParent = parent;
parent.myChildren[(j+1) % 2] = heapNode;
}
for (int j = heapNodes.size() / 2 - 1; j >= 0; j--) {
heapify(heapNodes.get(j));
}
root.myChildren[2] = heapNodes.get(0);
root.myChildren[2].myParent = root;
}
}
}
@@ -271,38 +269,37 @@ public class KShortestPathsFinder<Node> {
public Heap<Node> insert(HeapNode<Node> node) {
int pos = mySize + 1;
int pow = 1;
while (pos > pow << 2) {
while (pos >= pow << 2) {
pow <<= 1;
}
HeapNode<Node> place = myRoot;
HeapNode<Node> newRoot = myRoot.copy();
HeapNode<Node> place = newRoot;
List<HeapNode<Node>> parents = new ArrayList<HeapNode<Node>>();
while (true) {
parents.add(place);
final int ind = (pos & pow) != 0 ? 1 : 0;
if (pow == 1) {
HeapNode<Node> placeCopy = place.copy();
placeCopy.myChildren[ind] = node;
node.myParent = placeCopy;
place.myChildren[ind] = node;
break;
}
place = place.myChildren[ind];
HeapNode<Node> copy = place.myChildren[ind].copy();
place.myChildren[ind] = copy;
place = copy;
pow >>= 1;
}
while (true) {
final HeapNode<Node> parent = node.myParent;
if (parent == null || parent.myEdge.getDelta() < node.myEdge.getDelta()) {
for (int i = parents.size() - 1; i >= 0; i--) {
HeapNode<Node> parent = parents.get(i);
if (parent.myEdge.getDelta() < node.myEdge.getDelta()) {
break;
}
final HeapNode<Node> parentCopy = parent.copy();
final GraphEdge<Node> t = parentCopy.myEdge;
parentCopy.myEdge = node.myEdge;
final GraphEdge<Node> t = parent.myEdge;
parent.myEdge = node.myEdge;
node.myEdge = t;
final HeapNode<Node> t2 = parentCopy.myChildren[2];
parentCopy.myChildren[2] = node.myChildren[2];
final HeapNode<Node> t2 = parent.myChildren[2];
parent.myChildren[2] = node.myChildren[2];
node.myChildren[2] = t2;
node = parentCopy;
}
HeapNode<Node> newRoot = node;
while (newRoot.myParent != null) {
newRoot = newRoot.myParent;
node = parent;
}
return new Heap<Node>(mySize + 1, newRoot);
}
@@ -310,7 +307,6 @@ public class KShortestPathsFinder<Node> {
private static class HeapNode<Node> {
public HeapNode<Node>[] myChildren;
public HeapNode<Node> myParent;
public GraphEdge<Node> myEdge;
private HeapNode(GraphEdge<Node> edge) {
@@ -321,7 +317,6 @@ public class KShortestPathsFinder<Node> {
public HeapNode(HeapNode<Node> node) {
myEdge = node.myEdge;
myChildren = node.myChildren.clone();
myParent = node.myParent;
}
public HeapNode<Node> copy() {
platform/platform-tests/testSrc/com/intellij/util/graph/KShortestPathsFinderTest.java
+22
View File
@@ -136,7 +136,29 @@ public class KShortestPathsFinderTest extends GraphTestCase {
graph.put("f", "t");
graph.put("t", "");
doTest(graph, "sabct", "sadeft", "sabdeft", "sabcdeft");
}
public void testBigHeap() {
final Map<String, String> graph = new HashMap<String, String>();
graph.put("s", "lo");
graph.put("a", "tb");
graph.put("b", "t");
graph.put("c", "ad");
graph.put("d", "e");
graph.put("e", "b");
graph.put("f", "cg");
graph.put("g", "h");
graph.put("h", "d");
graph.put("i", "fj");
graph.put("j", "k");
graph.put("k", "g");
graph.put("l", "im");
graph.put("m", "n");
graph.put("n", "j");
graph.put("o", "p");
graph.put("p", "m");
graph.put("t", "");
doTest(graph, "slifcat", "slifcabt", "slifcdebt", "slifghdebt", "slijkghdebt", "slmnjkghdebt", "sopmnjkghdebt");
}
private static void doTest(Map<String, String> graph, String... expectedPaths) {