Problem:
Problem D: Long Distance Taxi

A taxi driver, Nakamura, was so delighted because he got a passenger who wanted to go to a
city thousands of kilometers away. However, he had a problem. As you may know, most taxis in
Japan run on liquefied petroleum gas (LPG) because it is cheaper than gasoline. There are more
than 50,000 gas stations in the country, but less than one percent of them sell LPG. Although
the LPG tank of his car was full, the tank capacity is limited and his car runs 10 kilometer per
liter, so he may not be able to get to the destination without filling the tank on the way. He
knew all the locations of LPG stations.
Your task is to write a program that finds the best way from the current location to the destination without running out of gas.

Input

The input consists of several datasets, and each dataset is in the following format.

N M cap

src dest

c1,1 c1,2 d1

c2,1 c2,2 d2

.

.

.

cN,1 cN,2 dN

s1

s2

.

.

.

sM

The first line of a dataset contains three integers (N, M, cap), where N is the number of roads
(1 ≤ N ≤ 3000),M is the number of LPG stations (1≤ M ≤ 300), and cap is the tank capacity
(1 ≤ cap ≤ 200) in liter. The next line contains the name of the current city (src) and the name
of the destination city (dest). The destination city is always different from the current city.
The following N lines describe roads that connect cities. The road i (1 ≤ i ≤ N) connects two
different cities ci,1 and ci,2 with an integer distance di (0 < di ≤ 2000) in kilometer, and he can
go from either city to the other. You can assume that no two different roads connect the same
pair of cities. The columns are separated by a single space. The next M lines (s1,s2,...,sM) indicate the names of the cities with LPG station.
You can assume that a city with LPG station has at least one road.

The name of a city has no more than 15 characters. Only English alphabet ('A' to 'Z' and 'a'
to 'z', case sensitive) is allowed for the name.

A line with three zeros terminates the input.

Output

For each dataset, output a line containing the length (in kilometer) of the shortest possible
journey from the current city to the destination city. If Nakamura cannot reach the destination,
output "-1" (without quotation marks). You must not output any other characters.
The actual tank capacity is usually a little bit larger than that on the specification sheet, so
you can assume that he can reach a city even when the remaining amount of the gas becomes
exactly zero. In addition, you can always fill the tank at the destination so you do not have to
worry about the return trip.

Sample Input

6 3 34
Tokyo Kyoto
Tokyo Niigata 335
Tokyo Shizuoka 174
Shizuoka Nagoya 176
Nagoya Kyoto 195
Toyama Niigata 215
Toyama Kyoto 296
Nagoya
Niigata
Toyama
6 3 30
Tokyo Kyoto
Tokyo Niigata 335
Tokyo Shizuoka 174
Shizuoka Nagoya 176
Nagoya Kyoto 195
Toyama Niigata 215
Toyama Kyoto 296
Nagoya
Niigata
Toyama
0 0 0

Output for the Sample Input

846
-1

Solution in JAVA (judge verdict: Accepted)


import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.HashMap;
import java.util.InputMismatchException;
import java.util.PriorityQueue;

public class Main {
	InputStream is;

	int __t__ = 1;
	int __f__ = 0;
	int __FILE_DEBUG_FLAG__ = __f__;
	String __DEBUG_FILE_NAME__ = "src/T";

	FastScanner in;
	PrintWriter out;

	class Edge {
		int to;
		int c;

		Edge(int to, int c) {
			this.to = to;
			this.c = c;
		}
		
		public String toString() {
			return "(" + to + " " + c + ")";
		}
	}
	
	int[] dijkstra(ArrayList<Edge>[] g, int from) {
		int n = g.length;
		final int[] res = new int[n];
		Arrays.fill(res, INF);
		res[from] = 0;
		
		PriorityQueue<Integer> pq = new PriorityQueue<Integer>(10, new Comparator<Integer>() {
			public int compare(Integer a, Integer b) {
				return res[a] - res[b];
			}
		});
		pq.add(from);
		
		while (!pq.isEmpty()) {
			int u = pq.poll();
			
			for (Edge e : g[u]) {
				if (res[u] + e.c < res[e.to]) {
					res[e.to] = res[u] + e.c;
					pq.add(e.to);
				}
			}
		}
		
		return res;
	}
	
	int INF = 100000000;
	HashMap<String, Integer> map = new HashMap<String, Integer>();
	@SuppressWarnings("unchecked")
	public void solve() {
		while (true) {
			int N = in.nextInt(), M = in.nextInt(), cap = in.nextInt() * 10;
			if (N == 0) break;
			
			map.clear();
			int size = 0;
			String src = in.next(), dst = in.next();
			map.put(src, size++);
			map.put(dst, size++);
			
			int[] u = new int[N];
			int[] v = new int[N];
			int[] d = new int[N];
			for (int i = 0; i < N; i++) {
				String from = in.next(), to = in.next();
				d[i] = in.nextInt();
				
				if (map.containsKey(from)) {
					u[i] = map.get(from);
				} else {
					u[i] = size;
					map.put(from, size++);
				}
				
				if (map.containsKey(to)) {
					v[i] = map.get(to);
				} else {
					v[i] = size;
					map.put(to, size++);
				}				
			}
			
			ArrayList<Edge>[] g = new ArrayList[size];
			for (int i = 0; i < size; i++)
				g[i] = new ArrayList<Edge>();
			
			for (int i = 0; i < N; i++) {
				g[u[i]].add(new Edge(v[i], d[i]));
				g[v[i]].add(new Edge(u[i], d[i]));
			}
			
			int[] s = new int[M + 2];
			for (int i = 1; i <= M; i++) {
				String name = in.next();
				s[i] = map.get(name);
			}
			int S = map.get(src), T = map.get(dst);
			s[0] = S;
			s[M+1] = T;

			ArrayList<Edge>[] minCost = new ArrayList[M+2];
			for (int i = 0; i < M + 2; i++) {
				minCost[i] = new ArrayList<Edge>();
			}

			for (int i = 0; i < M + 2; i++) {
				int[] cost = dijkstra(g, s[i]);
				for (int j = 0; j < M + 2; j++) {
					minCost[i].add(new Edge(j, (cost[s[j]] <= cap) ? cost[s[j]] : INF));
				}
			}

			int[] res = dijkstra(minCost, 0);
			System.out.println(res[M+1] == INF ? -1 : res[M+1]);
		}
	}

	public void run() {
		if (__FILE_DEBUG_FLAG__ == __t__) {
			try {
				is = new FileInputStream(__DEBUG_FILE_NAME__);
			} catch (FileNotFoundException e) {
				// TODO ????????????????????? catch ????????????
				e.printStackTrace();
			}
			System.out.println("FILE_INPUT!");
		} else {
			is = System.in;
		}
		in = new FastScanner(is);
		out = new PrintWriter(System.out);

		solve();
	}

	public static void main(String[] args) {
		new Main().run();
	}

	public void mapDebug(int[][] a) {
		System.out.println("--------map display---------");

		for (int i = 0; i < a.length; i++) {
			for (int j = 0; j < a[i].length; j++) {
				System.out.printf("%3d ", a[i][j]);
			}
			System.out.println();
		}

		System.out.println("----------------------------");
		System.out.println();
	}

	public void debug(Object... obj) {
		System.out.println(Arrays.deepToString(obj));
	}

	class FastScanner {
		private InputStream stream;
		private byte[] buf = new byte[1024];
		private int curChar;
		private int numChars;

		public FastScanner(InputStream stream) {
			this.stream = stream;
			//stream = new FileInputStream(new File("dec.in"));

		}

		int read() {
			if (numChars == -1)
				throw new InputMismatchException();
			if (curChar >= numChars) {
				curChar = 0;
				try {
					numChars = stream.read(buf);
				} catch (IOException e) {
					throw new InputMismatchException();
				}
				if (numChars <= 0)
					return -1;
			}
			return buf[curChar++];
		}

		boolean isSpaceChar(int c) {
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}

		boolean isEndline(int c) {
			return c == '\n' || c == '\r' || c == -1;
		}

		int nextInt() {
			return Integer.parseInt(next());
		}

		int[] nextIntArray(int n) {
			int[] array = new int[n];
			for (int i = 0; i < n; i++)
				array[i] = nextInt();

			return array;
		}

		int[][] nextIntMap(int n, int m) {
			int[][] map = new int[n][m];
			for (int i = 0; i < n; i++) {
				map[i] = in.nextIntArray(m);
			}
			return map;
		}

		long nextLong() {
			return Long.parseLong(next());
		}

		long[] nextLongArray(int n) {
			long[] array = new long[n];
			for (int i = 0; i < n; i++)
				array[i] = nextLong();

			return array;
		}

		long[][] nextLongMap(int n, int m) {
			long[][] map = new long[n][m];
			for (int i = 0; i < n; i++) {
				map[i] = in.nextLongArray(m);
			}
			return map;
		}

		double nextDouble() {
			return Double.parseDouble(next());
		}

		double[] nextDoubleArray(int n) {
			double[] array = new double[n];
			for (int i = 0; i < n; i++)
				array[i] = nextDouble();

			return array;
		}

		double[][] nextDoubleMap(int n, int m) {
			double[][] map = new double[n][m];
			for (int i = 0; i < n; i++) {
				map[i] = in.nextDoubleArray(m);
			}
			return map;
		}

		String next() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isSpaceChar(c));
			return res.toString();
		}

		String[] nextStringArray(int n) {
			String[] array = new String[n];
			for (int i = 0; i < n; i++)
				array[i] = next();

			return array;
		}

		String nextLine() {
			int c = read();
			while (isEndline(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isEndline(c));
			return res.toString();
		}
	}
}