Floyd弗洛伊德算法

先看懂如何使用

• 用Java实现一个地铁票价计算程序

• String station = "A1 A2 A3 A4 A5 A6 A7 A8 A9 T1 A10 A11 A12 A13 T2 A14 A15 A16 A17 A18 B1 B2 B3 B4 B5 T1 B6 B7 B8 B9 B10 T2 B11 B12 B13 B14 B15";

思路:step1: 设计为A1-A18, T1,T2,B1-B15个点

　　step2:35个点做为arr[35][35],将相邻的点A1-A2 ...赋值为1, T1和左右两点复制为1,

               自己_自己复制为0,

               不相邻值为1000(代表无穷大),A18_B1复制为1000

　　step 3

//Floyd算法求解
        for(int k=0; k<length; k++){
            for(int i=0; i<length; i++) {
                for(int j=0; j<length; j++) {
                    if((arr[i][k] + arr[k][j]) < arr[i][j]) {
                        arr[i][j] =  arr[i][k] + arr[k][j];
                    }
                }
            }
        }

package com.train;

import java.lang.reflect.Array;
import java.util.HashMap;
import java.util.Scanner;
import java.util.concurrent.ForkJoinPool;

public class TrainDemo {
    public static void main(String[] args) {


        String station = "A1 A2 A3 A4 A5 A6 A7 A8 A9 T1 A10 A11 A12 A13 T2 A14 A15 A16 A17 A18 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11 B12 B13 B14 B15";
        String[] stationarr = station.split("\s{1,}"); //length=37
        HashMap<String, Integer> uniMap = new HashMap<>();
        for (int i = 0; i < stationarr.length; i++) {

            uniMap.put(stationarr[i], i);
        }
        //distanceMap.put("T1")
        System.out.println(uniMap.toString());
        //创造一个2维数组,twoarr
        // 不能访问的值为@@无穷大
        //自己和自己直接为0;
        //

        Integer[][] twoarr = new Integer[stationarr.length][stationarr.length];
        for (int i = 0; i < stationarr.length; i++) {
            for (int j = 0; j < stationarr.length; j++) {
                if (i == j) {
                    twoarr[i][j] = 0;
                } else {
                    twoarr[i][j] = 1000;
                }
            }
        }

        for (int i = 0; i <stationarr.length-1 ; i++) {
            twoarr[i][i+1]=1;
            twoarr[i+1][i]=1;
        }
        //将能能到达的两点间设置为具体值
//


        twoarr[uniMap.get("A18").intValue()][uniMap.get("B1").intValue()]=1;
        twoarr[9][9]=0;
        twoarr[14][14]=0;
        twoarr[9][14]=0;
        twoarr[14][9]=0;
        //相通
        twoarr[9][24]=1;
        twoarr[24][9]=1;
        twoarr[9][25]=1;
        twoarr[25][9]=1;
        twoarr[14][29]=1;
        twoarr[29][14]=1;
        twoarr[14][30]=1;
        twoarr[30][14]=1;
        twoarr[uniMap.get("A18")][uniMap.get("B1")] = 1000;
        twoarr[uniMap.get("B1")][uniMap.get("A18")] = 1000;
        //t1=9 t2=14
//arr[stationMap.get("A1").intValue()][stationMap.get("A18").intValue()] = 1;
        for (int k = 0; k < 35; k++) {


            for (int i = 0; i <stationarr.length ; i++) {
                for (int j = 0; j <stationarr.length ; j++) {

                     if(twoarr[i][k]+twoarr[k][j]<twoarr[i][j]){
                         twoarr[i][j] = twoarr[i][k] + twoarr[k][j];
                     }
                }
            }
        }
        for (int i = 0; i < 35; i++) {
            for (int j = 0; j <35 ; j++) {
                System.out.print(twoarr[i][j]+" ");
            }
            System.out.println();

        }
        while (true){ String s = new Scanner(System.in).nextLine();
        String[] sarr= s.split("\s{1,}");
        System.out.println(twoarr[uniMap.get(sarr[0])][uniMap.get(sarr[1])]);
        }
    }
}

atzhang