package org.iaiai.suanfa; import java.util.ArrayList; /** * * <p> * Title: Dijkstra.java * </p> * <p> * E-Mail: [email protected] * </p> * <p> * QQ: 176291935 * </p> * <p> * Http: iaiai.iteye.com * </p> * <p> * Create time: 2011-8-5 * </p> * * @author 丸子 * @version 0.0.1 */ public class Dijkstra { static ArrayList<Side> map = null; static ArrayList<Integer> redAgg = null; static ArrayList<Integer> blueAgg = null; static Side[] parents = null; public static void main(String[] args) { // 初始化顶点集 int[] nodes = { 0, 1, 3, 2, 4, 5, 6 }; // 初始化有向权重图 map = new ArrayList<Side>(); map.add(new Side(0, 1, 10)); map.add(new Side(0, 3, 30)); map.add(new Side(0, 4, 100)); map.add(new Side(1, 2, 50)); map.add(new Side(2, 4, 10)); map.add(new Side(3, 2, 20)); map.add(new Side(3, 4, 60)); map.add(new Side(4, 5, 50)); map.add(new Side(3, 5, 60)); map.add(new Side(5, 6, 10)); map.add(new Side(3, 6, 80)); // 初始化已知最短路径的顶点集,即红点集,只加入顶点0 redAgg = new ArrayList<Integer>(); redAgg.add(nodes[0]); // 初始化未知最短路径的顶点集,即蓝点集 blueAgg = new ArrayList<Integer>(); for (int i = 1; i < nodes.length; i++) blueAgg.add(nodes[i]); // 初始化每个顶点在最短路径中的父结点,及它们之间的权重,权重-1表示无连通 parents = new Side[nodes.length]; parents[0] = new Side(-1, nodes[0], 0); for (int i = 0; i < blueAgg.size(); i++) { int n = blueAgg.get(i); parents[i + 1] = new Side(nodes[0], n, getWeight(nodes[0], n)); } // 找从蓝点集中找出权重最小的那个顶点,并把它加入到红点集中 while (blueAgg.size() > 0) { MinShortPath msp = getMinSideNode(); if (msp.getWeight() == -1) msp.outputPath(nodes[0]); else msp.outputPath(); int node = msp.getLastNode(); redAgg.add(node); // 如果因为加入了新的顶点,而导致蓝点集中的顶点的最短路径减小,则要重要设置 setWeight(node); } } /** */ /** * 得到一个节点的父节点 * * @param parents * @param node * @return */ public static int getParent(Side[] parents, int node) { if (parents != null) { for (Side nd : parents) { if (nd.getNode() == node) { return nd.getPreNode(); } } } return -1; } /** */ /** * 重新设置蓝点集中剩余节点的最短路径长度 * * @param preNode * @param map * @param blueAgg */ public static void setWeight(int preNode) { if (map != null && parents != null && blueAgg != null) { for (int node : blueAgg) { MinShortPath msp = getMinPath(node); int w1 = msp.getWeight(); if (w1 == -1) continue; for (Side n : parents) { if (n.getNode() == node) { if (n.getWeight() == -1 || n.getWeight() > w1) { n.setWeight(w1); n.setPreNode(preNode);// 重新设置顶点的父顶点 break; } } } } } } /** */ /** * 得到两点节点之间的权重 * * @param map * @param preNode * @param node * @return */ public static int getWeight(int preNode, int node) { if (map != null) { for (Side s : map) { if (s.getPreNode() == preNode && s.getNode() == node) return s.getWeight(); } } return -1; } /** */ /** * 从蓝点集合中找出路径最小的那个节点 * * @param map * @param blueAgg * @return */ public static MinShortPath getMinSideNode() { MinShortPath minMsp = null; if (blueAgg.size() > 0) { int index = 0; for (int j = 0; j < blueAgg.size(); j++) { MinShortPath msp = getMinPath(blueAgg.get(j)); if (minMsp == null || msp.getWeight() != -1 && msp.getWeight() < minMsp.getWeight()) { minMsp = msp; index = j; } } blueAgg.remove(index); } return minMsp; } /** */ /** * 得到某一节点的最短路径(实际上可能有多条,现在只考虑一条) * * @param node * @return */ public static MinShortPath getMinPath(int node) { MinShortPath msp = new MinShortPath(node); if (parents != null && redAgg != null) { for (int i = 0; i < redAgg.size(); i++) { MinShortPath tempMsp = new MinShortPath(node); int parent = redAgg.get(i); int curNode = node; while (parent > -1) { int weight = getWeight(parent, curNode); if (weight > -1) { tempMsp.addNode(parent); tempMsp.addWeight(weight); curNode = parent; parent = getParent(parents, parent); } else break; } if (msp.getWeight() == -1 || tempMsp.getWeight() != -1 && msp.getWeight() > tempMsp.getWeight()) msp = tempMsp; } } return msp; } }
package org.iaiai.suanfa; import java.util.ArrayList; /** * * <p> * Title: MinShortPath.java * </p> * <p> * E-Mail: [email protected] * </p> * <p> * QQ: 176291935 * </p> * <p> * Http: iaiai.iteye.com * </p> * <p> * Create time: 2011-8-5 * </p> * * @author 丸子 * @version 0.0.1 */ public class MinShortPath { private ArrayList<Integer> nodeList;// 最短路径集 private int weight;// 最短路径 public MinShortPath(int node) { nodeList = new ArrayList<Integer>(); nodeList.add(node); weight = -1; } public ArrayList<Integer> getNodeList() { return nodeList; } public void setNodeList(ArrayList<Integer> nodeList) { this.nodeList = nodeList; } public void addNode(int node) { if (nodeList == null) nodeList = new ArrayList<Integer>(); nodeList.add(0, node); } public int getLastNode() { int size = nodeList.size(); return nodeList.get(size - 1); } public int getWeight() { return weight; } public void setWeight(int weight) { this.weight = weight; } public void outputPath() { outputPath(-1); } public void outputPath(int srcNode) { String result = "["; if (srcNode != -1) nodeList.add(srcNode); for (int i = 0; i < nodeList.size(); i++) { result += "" + nodeList.get(i); if (i < nodeList.size() - 1) result += ","; } result += "]:" + weight; System.out.println(result); } public void addWeight(int w) { if (weight == -1) weight = w; else weight += w; } }
package org.iaiai.suanfa; /** * * <p> * Title: Side.java * </p> * <p> * E-Mail: [email protected] * </p> * <p> * QQ: 176291935 * </p> * <p> * Http: iaiai.iteye.com * </p> * <p> * Create time: 2011-8-5 * </p> * * @author 丸子 * @version 0.0.1 */ public class Side { private int preNode; // 前向节点 private int node;// 后向节点 private int weight;// 权重 public Side(int preNode, int node, int weight) { this.preNode = preNode; this.node = node; this.weight = weight; } public int getPreNode() { return preNode; } public void setPreNode(int preNode) { this.preNode = preNode; } public int getNode() { return node; } public void setNode(int node) { this.node = node; } public int getWeight() { return weight; } public void setWeight(int weight) { this.weight = weight; } }
输出:
引用
[0,1]:10
[0,3]:30
[0,3,2]:50
[0,3,2,4]:60
[0,3,5]:90
[0,3,5,6]:100
[0,3]:30
[0,3,2]:50
[0,3,2,4]:60
[0,3,5]:90
[0,3,5,6]:100