ThoughtWorks HomeWork

记ThoughtWorks一道HomeWork

The local commuter railroad services a number of towns in Kiwiland.  Because of monetary concerns, all of the tracks are 'one-way.'  That is, a route from Kaitaia to Invercargill does not imply the existence of a route from Invercargill to Kaitaia.  In fact, even if both of these routes do happen to exist, they are distinct and are not necessarily the same distance!

 

The purpose of this problem is to help the railroad provide its customers with information about the routes.  In particular, you will compute the distance along a certain route, the number of different routes between two towns, and the shortest route between two towns.

 

Input:  A directed graph where a node represents a town and an edge represents a route between two towns.  The weighting of the edge represents the distance between the two towns.  A given route will never appear more than once, and for a given route, the starting and ending town will not be the same town.

 

Output: For test input 1 through 5, if no such route exists, output 'NO SUCH ROUTE'.  Otherwise, follow the route as given; do not make any extra stops!  For example, the first problem means to start at city A, then travel directly to city B (a distance of 5), then directly to city C (a distance of 4).

1. The distance of the route A-B-C.
2. The distance of the route A-D.
3. The distance of the route A-D-C.
4. The distance of the route A-E-B-C-D.
5. The distance of the route A-E-D.
6. The number of trips starting at C and ending at C with a maximum of 3 stops.  In the sample data below, there are two such trips: C-D-C (2 stops). and C-E-B-C (3 stops).
7. The number of trips starting at A and ending at C with exactly 4 stops.  In the sample data below, there are three such trips: A to C (via B,C,D); A to C (via D,C,D); and A to C (via D,E,B).
8. The length of the shortest route (in terms of distance to travel) from A to C.
9. The length of the shortest route (in terms of distance to travel) from B to B.
10. The number of different routes from C to C with a distance of less than 30.  In the sample data, the trips are: CDC, CEBC, CEBCDC, CDCEBC, CDEBC, CEBCEBC, CEBCEBCEBC.

 

Test Input:

For the test input, the towns are named using the first few letters of the alphabet from A to D.  A route between two towns (A to B) with a distance of 5 is represented as AB5.

Graph: AB5, BC4, CD8, DC8, DE6, AD5, CE2, EB3, AE7

Expected Output:

Output #1: 9

Output #2: 5

Output #3: 13

Output #4: 22

Output #5: NO SUCH ROUTE

Output #6: 2

Output #7: 3

Output #8: 9

Output #9: 9

Output #10: 7

public class HomeWork {

    /**
     * 使用起始站和终点站位节点创建一个二维数组
     */
    private static int[][] arrs = {
            {0,5,0,5,7},
            {0,0,4,0,0},
            {0,0,0,8,2},
            {0,0,8,0,6},
            {0,3,0,0,0}
    };

    /**
     * 最短路径
     */
    private static String shortedPath = "";

    /**
     * 最短路径值
     */
    private static int shortedVal = Integer.MAX_VALUE;

    public static void main(String[] args){
        List list1 = new ArrayList();
        list1.add("A");
        list1.add("B");
        list1.add("C");
        String result1 = HomeWork.getRoute(list1);//Test1
        System.out.println(result1);

        List list2 = new ArrayList();
        list2.add("A");
        list2.add("D");
        String result2 = HomeWork.getRoute(list2);//Test2
        System.out.println(result2);

        List list3 = new ArrayList();
        list3.add("A");
        list3.add("D");
        list3.add("C");
        String result3 = HomeWork.getRoute(list3);//Test3
        System.out.println(result3);

        List list4 = new ArrayList();
        list4.add("A");
        list4.add("E");
        list4.add("B");
        list4.add("C");
        list4.add("D");
        String result4 = HomeWork.getRoute(list4);//Test4
        System.out.println(result4);

        List list5 = new ArrayList();
        list5.add("A");
        list5.add("E");
        list5.add("D");
        String result5 = HomeWork.getRoute(list5);//Test5
        System.out.println(result5);

        List list6 = new ArrayList<>();
        List pathList6 = HomeWork.cTocLessThen("C", "C", 3, list6);//Test6
        System.out.println(pathList6.size());

        int result7 = HomeWork.aTocWith("A", "C", 4);//Test7
        System.out.println(result7);

        int result8 = HomeWork.aTocShorted("A", "C", 0);//Test8
        System.out.println(result8);

        int result9 = HomeWork.aTocShorted("B", "B", 0);//Test9
        System.out.println(result9);

        List list10 = new ArrayList<>();
        List pathList10 = HomeWork.cTocValLessThen("C", "C", 0,list10);//Test10
        System.out.println(pathList10.size());
    }

    /**
     * Test1.The distance of the route A-B-C.
     * Test2.The distance of the route A-D.
     * Test3.The distance of the route A-D-C.
     * Test4.The distance of the route A-E-B-C-D.
     * Test5.The distance of the route A-E-D.
     */
    private static String getRoute(List list){
        int result = 0;
        String resultStr = "";
        for (int i = 0; i < list.size() - 1; i++){
            int m = strToInt(list.get(i));
            int n = strToInt(list.get(i + 1));
            int[] arr = arrs[m];
            int path = arr[n];
            if (path > 0){
                result += path;
            } else {
                return "NO SUCH ROUTE";
            }
        }
        if (result > 0){
            resultStr = result + "";
        }else {
            resultStr = "NO SUCH ROUTE";
        }
        return resultStr;
    }

    /**
     * Test6 The number of trips starting at C and ending at C with a maximum of 3 stops.  In the sample data below, there are two such trips: C-D-C (2 stops). and C-E-B-C (3 stops).
     * @param start 起点
     * @param path 路径
     * @param maxPath 最大步数
     * @param list 路径列表
     * @return
     */
    private static List cTocLessThen(String start, String path, int maxPath,List list) {
        if (path.length() - 1 > maxPath){
            return list;
        }
        if (path.length() > 1 && path.endsWith(start)) {
//            System.out.println(path);
            list.add(path);
        }
        char lastChar = path.charAt(path.length()-1);
        int m = lastChar - 'A';
        for (int i = 0; i < arrs[m].length; i++){
            char ch = (char) (i + 'A');
            if (arrs[m][i] > 0){
                cTocLessThen(start,path + ch,maxPath,list);
            }
        }
        return list;
    }

    /**
     * Test7. The number of trips starting at A and ending at C with exactly 4 stops.  In the sample data below, there are three such trips: A to C (via B,C,D); A to C (via D,C,D); and A to C (via D,E,B).
     * @param start 起点
     * @param end 终点
     * @param step 步数
     * @return
     */
    private static int aTocWith(String start,String end,int step){
        int result = 0;
        String lastRoute = start;
        for (int i = 0; i < step; i++){
            String route = "";
            for (int j = 0; j < lastRoute.length(); j++){
                char ch = lastRoute.charAt(j);
                int m = ch - 'A';

                for (int n = 0; n < arrs[m].length; n++){
                    if (arrs[m][n] > 0){
                        route = route + (char)(n + 'A');
                    }
                }
            }
            lastRoute = route;
        }
        result = lastRoute.split(end).length - 1;
        return result;
    }

    /**
     * 8. The length of the shortest route (in terms of distance to travel) from A to C.
     * 9. The length of the shortest route (in terms of distance to travel) from B to B.
     * @param path 以path为起点的路径
     * @param end 终点
     * @param pathVal 路径的值
     * @return
     */
    private static int aTocShorted(String path,String end,int pathVal){
        if (path.endsWith(end) && pathVal < shortedVal && pathVal > 0) {
            shortedPath = path;
            shortedVal = pathVal;
            return pathVal;
        }
        char lastChar = path.charAt(path.length() - 1);
        int m = lastChar - 'A';
        for (int i = 0; i < arrs[m].length; i++){
            char ch = (char) (i + 'A');
            int value = arrs[m][i];
            if (value > 0){
                if (path.indexOf(ch) > 0){
                    continue;
                }else {
                    aTocShorted(path + ch,end,pathVal + value);
                }

            }
        }
        return shortedVal;
    }

    /**
     * 10. The number of different routes from C to C with a distance of less than 30.  In the sample data, the trips are: CDC, CEBC, CEBCDC, CDCEBC, CDEBC, CEBCEBC, CEBCEBCEBC.
     * @param path 路径
     * @param end 终点
     * @param pathVal 路径值
     * @param list 路径列表
     * @return
     */
    private static List cTocValLessThen(String path,String end,int pathVal,List list) {
        if (pathVal >= 30){
            return list;
        }
        if (pathVal > 0 && path.endsWith(end)) {
//            System.out.println(path);
            list.add(path);
        }
        char lastChar = path.charAt(path.length() - 1);
        int m = lastChar - 'A';
        for (int i = 0; i < arrs[m].length; i++) {
            char newChar = (char) (i + 'A');
            int newCost = arrs[m][i];
            if (newCost > 0) {
                cTocValLessThen(path + newChar, end, pathVal + newCost,list);
            }
        }
        return list;
    }

    /**
     * 将字符串转换成ASCII对应的数字获取二维数组坐标
     * @param str
     * @return
     */
    public static int strToInt(String str){
        char[] chars = str.toCharArray();
        int i = 0;
        for (char ch : chars){
            i = ch - 'A';
        }
        return i;
    }
}