單源最短路徑，關(guān)于這個(gè)問題的貪心算有點(diǎn)不好理解，分析后續(xù)補(bǔ)充，代碼也需要后續(xù)優(yōu)化，便于理解

package test;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

/**

* Created by saishangmingzhu on 2018/12/3.

* 單源最短路徑

*/

public class SingleSourceShortestPath {

public static void main(String[] arg) {

new SingleSourceShortestPath().greedy();

}

/**

* 貪心算法

*/

public void greedy(){

//【1】創(chuàng)建有向圖

List pointList=new ArrayList<>();

pointList.add(new Point("A",0));

pointList.add(new Point("B",1));

pointList.add(new Point("C",2));

pointList.add(new Point("D",3));

pointList.add(new Point("E",4));

Map pathMap=new HashMap<>();

pathMap.put("AB",10);

pathMap.put("AD",30);

pathMap.put("AE",100);

pathMap.put("BC",50);

pathMap.put("CE",10);

pathMap.put("DC",20);

pathMap.put("DE",60);

//【2】從源頂點(diǎn)計(jì)算距離

// 源頂點(diǎn)為A

int[] dist=new int[pointList.size()];

for (int i=1;i

dist[i]=Integer.MAX_VALUE;

}

List resultList=new ArrayList<>();

Point first=pointList.get(0);

pointList.remove(0);

while (pointList.size()>0){

int min=10000;

Point minP=null;

for (int i=0;i

Point p = pointList.get(i);

String key = first.getName() + p.getName();

if (pathMap.containsKey(key)) {

int v = pathMap.get(key);

if (dist[p.getIndex()] > v + dist[first.getIndex()]) {

dist[p.getIndex()] = v + dist[first.getIndex()];

if (min>v + dist[first.getIndex()]){

min=v + dist[first.getIndex()];

minP=p;

}

}

}

else {

if (min>dist[p.getIndex()]){

min=dist[p.getIndex()];

minP=p;

}

}

}

resultList.add(minP);

pointList.remove(minP);

first=minP;

}

for (int i:dist)

System.out.println(i);

}

}

class Point{

String name;

int index;

public Point(String name, int index) {

this.name = name;

this.index = index;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public int getIndex() {

return index;

}

public void setIndex(int index) {

this.index = index;

}

}

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