POJ 1364差分约束

给出n个变量，m个约束公式 Sa + Sa+1 + .... + Sa+b < ki or > ki ,叫你判断是否存在着解满足这m组约束公式。

Sa + Sa+1   +   .+ Sa+b =  Sum[a+b] - Sum[a-1]  . 注意加入源点n+1 。

public class Main {public static void main(String[] args) throws UnsupportedEncodingException {new Task().solve();}}class Task {class Node {int w;int v;Node(int v, int w) {this.w = w;this.v = v;}}List<Node>[] adj;final int inf = 1000000000;boolean spfa(int start, int n) {int[] dist = new int[n + 1];int[] inqTime = new int[n + 1];boolean[] inq = new boolean[n + 1];Arrays.fill(dist, inf);Arrays.fill(inqTime, 0);Arrays.fill(inq, false);dist[start] = 0;inq[start] = true;Queue<Integer> q = new LinkedList<Integer>();q.offer(start);while (! q.isEmpty()) {int u = q.poll();inq[u] = false;for (Node next : adj[u]) {int v = next.v;int w = next.w;if (dist[u] + w < dist[v]) {dist[v] = dist[u] + w;if (!inq[v]) {inq[v] = true;if (++inqTime[v] > n)return false;q.offer(v) ;}}}}return true;}void solve() {while (true) {int n = in.nextInt();if (n == 0)break;int m = in.nextInt();adj = new List[n + 2];for (int i = 0; i <= n+1; i++)adj[i] = new ArrayList<Node>();while (m-- > 0) {int si = in.nextInt();int ni = in.nextInt();String oi = in.next();int ki = in.nextInt();if ("gt".equals(oi)) {adj[si + ni].add(new Node(si - 1, -ki - 1));} else {adj[si - 1].add(new Node(si + ni, ki - 1));}}for (int i = 0; i <= n; i++)adj[n+1].add(new Node(i, 0));out.println(spfa(n+1, n+2) ? "lamentable kingdom": "successful conspiracy");}out.flush();}InputReader in = new InputReader(System.in);PrintWriter out = new PrintWriter(System.out);}class InputReader {public BufferedReader reader;public StringTokenizer tokenizer;public InputReader(InputStream stream) {reader = new BufferedReader(new InputStreamReader(stream), 32768);tokenizer = new StringTokenizer("");}private void eat(String s) {tokenizer = new StringTokenizer(s);}public String nextLine() {try {return reader.readLine();} catch (Exception e) {return null;}}public boolean hasNext() {while (!tokenizer.hasMoreTokens()) {String s = nextLine();if (s == null)return false;eat(s);}return true;}public String next() {hasNext();return tokenizer.nextToken();}public int nextInt() {return Integer.parseInt(next());}public long nextLong() {return Long.parseLong(next());}public double nextDouble() {return Double.parseDouble(next());}public BigInteger nextBigInteger() {return new BigInteger(next());}}