【HDOJ】3660 Alice and Bob's Trip

就是一个基本的dfs。可关键问题是c/c++/g++光输入就超时了。还是写java过的，毕竟时限4s。都放弃希望了，没想到还真过了。

import java.lang.*;
import java.io.*;
import java.util.*;


public class Main {
    
    public static void main(String[] args) throws java.lang.Exception {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        TaskA solver = new TaskA();
        solver.solve(in, out);
        out.close();
    }
}

class TaskA {
    public final static int maxv = (int)(5e5+5);
    public final static int INF = 0x3f3f3f3f;
    int[] V = new int[maxv];
    int[] W = new int[maxv];
    int[] nxt = new int[maxv];
    int[] head = new int[maxv];
    int m, n, L, R;
    
    void init() {
        m = 0;
        Arrays.fill(head, -1);
    }
    
    void addEdge(int u, int v, int w) {
        V[m] = v;
        W[m] = w;
        nxt[m] = head[u];
        head[u] = m++;
    }
    
    public void solve(InputReader in, PrintWriter out) {
        int i;
        int u, v, w;
        int ans;
        
        while (true) {
            try {
                n = in.nextInt();
            } catch (RuntimeException e) {
                break;
            }
            L = in.nextInt();
            R = in.nextInt();
            init();
            for (i=1; i<n; ++i) {
                u = in.nextInt();
                v = in.nextInt();
                w = in.nextInt();
                addEdge(u, v, w);
            }
            ans = dfs(0, 0, 0);
            if (ans == INF)
                out.println("Oh, my god!");
            else
                out.println(ans);
        }
    }
    
    private int dfs(int u, int len, int now) {
        int ans = -1;
        
        if (head[u] == -1)
            return 0;
        int i, v, w;
        
        for (i=head[u]; i!=-1; i=nxt[i]) {
            v = V[i];
            w = W[i];
            int tmp = dfs(v, len+w, now^1) + w;
            if (tmp == INF)
                continue;
            if (tmp>=L-len && tmp<=R-len) {
                if (now == 0) {
                    if (ans==-1 || tmp>ans)
                        ans = tmp;
                } else {
                    if (ans==-1 || tmp<ans)
                        ans = tmp;
                }
            }
        }
        
        if (ans == -1)
            return INF;
        return ans;
    }
}

class InputReader {
    public BufferedReader reader;
    public StringTokenizer tokenizer;
    
    public InputReader(InputStream stream) {
        reader = new BufferedReader(new InputStreamReader(stream), 32768);
        tokenizer = null;
    }
    
    public String next() {
        while (tokenizer==null || !tokenizer.hasMoreTokens()) {
            try {
                tokenizer = new StringTokenizer(reader.readLine());
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return tokenizer.nextToken();
    }
    
    public int nextInt() {
        return Integer.parseInt(next());
    }
}