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Copy pathFindSSCsInGraph.java
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321 lines (282 loc) · 9.57 KB
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package basicAlgorithm;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.util.BitSet;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedList;
public class FindSSCsInGraph {
/**
* @param args
*/
private HashMap<Integer, LinkedList<Integer>> originalGraph; // keep
// original
// Graph,
// each
// vertex
// corresponds to an index and
// the content of that index is
// a BitSet of node size N. If
// there is edge exist between
// vertices s and v, then the
// bit of v would be true on
// originalGraph[s]
private HashMap<Integer, LinkedList<Integer>> reversedGraph;
private int totalNumNodes; // number of total nodes
private BitSet nodesStatus; // keep 1/0 for nodes explored/not
private int[] nodesFinishtime; // keep finishing time for all
// nodes in first
private int[] nodesSortedbyFt; // sorted nodes by finishing time increasing
// order
private int[] nodesStack; // simulate stack for nodes when doing dfs
private int[] sortedSCCsSize; // size of each SCCs;
// time reversed graph dfs
private HashMap<Integer, LinkedList<Integer>> sccsOfLeader; // leader is the
// key, nodes
// belongs to
// the key in
// the linked
// list;
private int curFinishTime; // global, current f(n) for first DFS loop
private int curLeader; // global, current Leader for 2nd DFS loop
private int topOfStack; // the pointer to the top of the stack in array
// nodesStack;
public FindSSCsInGraph(int numNodes, String filename) throws IOException {
originalGraph = new HashMap<Integer, LinkedList<Integer>>();
reversedGraph = new HashMap<Integer, LinkedList<Integer>>();
nodesStatus = new BitSet(numNodes);
nodesFinishtime = new int[numNodes];
nodesSortedbyFt = new int[numNodes];
nodesStack = new int[numNodes];
sortedSCCsSize = new int[numNodes];
sccsOfLeader = new HashMap<Integer, LinkedList<Integer>>();
totalNumNodes = numNodes;
curFinishTime = 1;
curLeader = -1;
topOfStack = -1;
for (int i = 0; i < numNodes; i++) {
originalGraph.put(i, new LinkedList<Integer>());
reversedGraph.put(i, new LinkedList<Integer>());
nodesFinishtime[i] = 0;
nodesSortedbyFt[i] = i; // initially set to be node's natural order
nodesStack[i] = -1;
}
readFileIntoMemory(filename, 100);
}
// push vertex into stack
public void pushToStack(int nodeIndex) {
topOfStack++;
nodesStack[topOfStack] = nodeIndex;
}
// pop the top out of stack
public void popFromStack() {
nodesStack[topOfStack] = -1;
topOfStack--;
}
public void readFileIntoMemory(String fileName, int lineNum)
throws IOException {
File file = new File(fileName);
BufferedReader br = new BufferedReader(new FileReader(file));
String line = br.readLine();
int headVertex = 0;
int tailVertex = 0;
// int lineNo =0;
while (line != null) {
// lineNo++;
String[] vertexRow = line.split(" ");
headVertex = Integer.parseInt(vertexRow[0]);
tailVertex = Integer.parseInt(vertexRow[1]);
// set the bit in originalGraph for index headVertex
// initialize originalGraph and nodesFinishtime;
LinkedList<Integer> tmp = originalGraph.get(headVertex - 1);
tmp.add(tailVertex - 1);
// set the bit in reversedGraph for index tailVertex
LinkedList<Integer> tmp2 = reversedGraph.get(tailVertex - 1);
tmp2.add(headVertex - 1);
line = br.readLine();
}
br.close();
}
public void firstDFSwithReversedG() {
for (int fromNode = 0; fromNode < totalNumNodes; fromNode++) {
// if not explored then go ahead, otherwise break
if (!nodesStatus.get(fromNode)) {
DFSforReversedG(fromNode);
}
}
}
public void DFSforReversedG(int nodeIndex) {
// push to stack, and mark explored;
pushToStack(nodeIndex);
nodesStatus.set(nodeIndex);
// printNodesStack();
// find next node this node has an directed edge to,that's not explored
// yet and do DFS on it, startBit to mark the index from which we
// should search for next neighbor node in the bitSet
int toNode = -1;
LinkedList<Integer> neighbors = reversedGraph.get(nodeIndex);
for (int i = 0; i < neighbors.size(); i++) {
toNode = neighbors.get(i);
if (!nodesStatus.get(toNode)) { // if neighbor has not been explored
DFSforReversedG(toNode);
}
}
// searched till last node;
popFromStack();
nodesFinishtime[nodeIndex] = curFinishTime;
curFinishTime++;
}
public void DFSforG(int nodeIndex) {
// push to stack, and mark explored;
pushToStack(nodeIndex);
nodesStatus.set(nodeIndex);
// find next node this node has an directed edge to,that's not explored
// yet and do DFS on it, startBit to mark the index from which we
// should search for next neighbor node in the bitSet
int toNode = -1;
LinkedList<Integer> neighbors = originalGraph.get(nodeIndex);
for (int i = 0; i < neighbors.size(); i++) {
toNode = neighbors.get(i);
if (!nodesStatus.get(toNode)) { // if neighbor has not been explored
DFSforG(toNode);
}
}
popFromStack();
sccsOfLeader.get(curLeader).add(nodeIndex);
}
// before doing this , make sure to reset the nodesStatus array and
// nodesStack
public void secondDFSwithG() {// nodesSortedbyFt is in f(n) increasing
// order, so get from the last
for (int fromNode = totalNumNodes - 1; fromNode > 0; fromNode--) {
curLeader = nodesSortedbyFt[fromNode];
// if not explored then go ahead, otherwise break
if (!nodesStatus.get(curLeader)) {
// curLeader = nodesSortedbyFt[fromNode]; // is 1 less than real
// node No.
// create the list with current node as leader
sccsOfLeader.put(curLeader, new LinkedList<Integer>());
DFSforG(curLeader);
}
}
}
// basically when sorting the nodesFinishtime, sorting the nodesSortedbyFt
// the same way, because they're corresponding to each other;
public void sortNodesByFinishingTime() {
ArraySort.quickSort2(nodesFinishtime, nodesSortedbyFt, 0,
totalNumNodes - 1);
// for(int i=0;i<totalNumNodes-1;i++){
// for(int j=i+1; j<totalNumNodes;j++){
// if(nodesFinishtime[i]<nodesFinishtime[j]){
// int tmp = nodesFinishtime[j];
// nodesFinishtime[j]=nodesFinishtime[i];
// nodesFinishtime[i]=tmp;
//
// int tmp2 = nodesSortedbyFt[j];
// nodesSortedbyFt[j]=nodesSortedbyFt[i];
// nodesSortedbyFt[i]=tmp2;
// }
// }
// }
//
// ArraySort.quickSort2(nodesFinishtime, nodesSortedbyFt, 0,
// totalNumNodes - 1);
// ArraySort.printArray(totalNumNodes, nodesFinishtime);
// ArraySort.printArray(totalNumNodes, nodesSortedbyFt);
}
public void printSccs() {
Iterator<Integer> it = sccsOfLeader.keySet().iterator();
int j = 0;
while (it.hasNext() && j < 10) {
int leaderVertex = it.next();
System.out.print((leaderVertex + 1) + ":");
for (int i = 0; i < sccsOfLeader.get(leaderVertex).size(); i++) {
System.out.print((sccsOfLeader.get(leaderVertex).get(i) + 1)
+ ",");
}
System.out.println();
j++;
}
}
public void printSizeOfSccs(int length, int dec_flag) {
for (int i = 0; i < 100; i++) {
if (dec_flag>0)
System.out.print(sortedSCCsSize[length-1-i] + " ");
else
System.out.print(sortedSCCsSize[i] + " ");
}
}
public void sortSccsBySize() {
Iterator<Integer> it = sccsOfLeader.keySet().iterator();
int i = 0;
while (it.hasNext()) {
int leaderVertex = it.next();
int sizeOfSccs = sccsOfLeader.get(leaderVertex).size();
sortedSCCsSize[i] = sizeOfSccs;
i++;
}
// sorting the array
int length = i;
System.out.println("length=" + length);
printSizeOfSccs(length, 0);
ArraySort.quickSort(sortedSCCsSize, 0, length - 1);
printSizeOfSccs(length, 1);
// for(int j=0;i<length-1;j++){
// for(int k=j+1;k<length;k++){
// if(sortedSCCsSize[j]<sortedSCCsSize[k]){
// int tmp = sortedSCCsSize[k];
// sortedSCCsSize[k] =sortedSCCsSize[j];
// sortedSCCsSize[j] =tmp;
// }
// }
// }
}
public void printNodesStack() {
for (int i = 0; i < topOfStack; i++) {
System.out.print((nodesStack[i] + 1) + " ");
if (i % 100 == 0)
System.out.println();
}
}
public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
FindSSCsInGraph obj = new FindSSCsInGraph(875714, "../SCC.txt");
// FindSSCsInGraph obj = new FindSSCsInGraph(6, "testSCC");
// FindSSCsInGraph obj2 = new FindSSCsInGraph(5, "RevtestSCC");
// System.out.println(obj.originalGraph.keySet().size());
// Iterator<Integer> it = obj.originalGraph.keySet().iterator();
// int i=0;
// while (it.hasNext() && i<=100) {
// int curVertex = it.next();
// int neighborSize = obj.originalGraph.get(curVertex).size();
// System.out.println(curVertex+":"+neighborSize+" ");
// i++;
// }
obj.firstDFSwithReversedG();
// ArraySort.printArray(10, obj.nodesFinishtime);
// System.out.println("----------------------------");
// ArraySort.printArray(6, obj.nodesSortedbyFt);
// System.out.println("----------------------------");
obj.sortNodesByFinishingTime();
// ArraySort.printArray(10, obj.nodesFinishtime);
// System.out.println("----------------------------");
// ArraySort.printArray(10, obj.nodesSortedbyFt);
obj.nodesStatus.clear();
obj.secondDFSwithG();
//
obj.sortSccsBySize();
// obj.printSizeOfSccs();
// System.out.println("------------------");
// obj2.firstDFSwithReversedG();
// //ArraySort.printArray(15, obj.nodesFinishtime);
// //ArraySort.printArray(6, obj.nodesSortedbyFt);
//
// obj2.sortNodesByFinishingTime();
// obj2.nodesStatus.clear();
// obj2.secondDFSwithG();
//
// obj2.printSccs();
}
}