package abc;
//package sinboy.datastructure;
import java.util.ArrayList;
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, 2, 3, 4, 5 };
// 初始化有向权重图
map = new ArrayList<Side>();
map.add(new Side(0, 2, 10));
map.add(new Side(0, 4, 30));
map.add(new Side(0, 5, 100));
map.add(new Side(1, 2, 5));
map.add(new Side(2, 3, 50));
map.add(new Side(3, 5, 10));
map.add(new Side(4, 3, 20));
map.add(new Side(4, 5, 60));
// 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;
}
}