挑战程序竞赛系列（78）：4.3 2-SAT（2）

AND
a b 
0 0 0
0 1 0
1 0 0
1 1 1

给定c = 1，说明 0-0，0-1，1-0的关系矛盾，据此加边：
2 * a， 2 * b 等价于 0
2 * a + 1 , 2 * b + 1等价于 1

scc.add(2 * a, 2 * b + 1);
scc.add(2 * b, 2 * a + 1);
scc.add(2 * a, 2 * b);
scc.add(2 * b + 1, 2 * a + 1);
scc.add(2 * a + 1, 2 * b + 1);
scc.add(2 * b, 2 * a);

给定c = 0，说明 1-1关系矛盾，据此加边：
scc.add(2 * a + 1, 2 * b);
scc.add(2 * b + 1, 2 * a);

异或，或同理。

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.StringTokenizer;

public class Main{

    String INPUT = "./data/judge/201709/P3678.txt";

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

    class SCC {
        static final int MAX_V = 1000 + 8;
        List<Integer>[] g  = new List[MAX_V];
        List<Integer>[] rg = new List[MAX_V];
        List<Integer> po   = new ArrayList<Integer>();
        boolean[] used = new boolean[MAX_V];
        int[] cmp = new int[MAX_V];
        int V;

        SCC(int V) {
            this.V = V;
            po = new ArrayList<Integer>();
            Arrays.fill(used, false);
            for (int i = 0; i < V; ++i) g[i]  = new ArrayList<Integer>();
            for (int i = 0; i < V; ++i) rg[i] = new ArrayList<Integer>();
        }

        void add(int from, int to) {
            g[from].add(to);
            rg[to].add(from);
        }

        void dfs(int v) {
            used[v] = true;
            for (int u : g[v]) {
                if (!used[u]) dfs(u);
            }
            po.add(v);
        }

        void rdfs(int v, int k) {
            used[v] = true;
            cmp[v]  = k;
            for (int u : rg[v]) {
                if (!used[u]) rdfs(u, k);
            }
        }

        int kosarajuSCC() {
            for (int v = 0; v < V; ++v) {
                if (!used[v]) dfs(v);
            }
            Arrays.fill(used, false);
            int k = 0;
            for (int i = po.size() - 1; i >= 0; --i) {
                int v = po.get(i);
                if (!used[v]) rdfs(v, k++);
            }
            return k;
        }

    }

    void read() {
        int N = ni();
        int M = ni();
        SCC scc = new SCC(N * 2);
        for (int i = 0; i < M; ++i) {
            int a = ni();
            int b = ni();
            int c = ni();
            String op = ns();
            if (op.equals("AND")) {
                if (c == 0) {
                    scc.add(2 * a + 1, 2 * b);
                    scc.add(2 * b + 1, 2 * a);
                }
                else {
                    scc.add(2 * a, 2 * b + 1);
                    scc.add(2 * b, 2 * a + 1);
                    scc.add(2 * a, 2 * b);
                    scc.add(2 * b + 1, 2 * a + 1);
                    scc.add(2 * a + 1, 2 * b + 1);
                    scc.add(2 * b, 2 * a);
                }
            }
            else if (op.equals("OR")) {
                if (c == 0) {
                    scc.add(2 * a, 2 * b);
                    scc.add(2 * b + 1, 2 * a + 1);
                    scc.add(2 * a + 1, 2 * b + 1);
                    scc.add(2 * b, 2 * a);
                    scc.add(2 * a + 1, 2 * b);
                    scc.add(2 * b + 1, 2 * a);
                }
                else {
                    scc.add(2 * a, 2 * b + 1);
                    scc.add(2 * b, 2 * a + 1);
                }
            }
            else {
                if (c == 0) {
                    scc.add(2 * a, 2 * b);
                    scc.add(2 * b + 1, 2 * a + 1);
                    scc.add(2 * a + 1, 2 * b + 1);
                    scc.add(2 * b, 2 * a);
                }
                else {
                    scc.add(2 * a, 2 * b + 1);
                    scc.add(2 * b, 2 * a + 1);
                    scc.add(2 * a + 1, 2 * b);
                    scc.add(2 * b + 1, 2 * a);
                }
            }
        }

        scc.kosarajuSCC();
        for (int i = 0; i < N; ++i) {
            if (scc.cmp[2 * i] == scc.cmp[2 * i + 1]) {
                out.println("NO");
                return;
            }
        }
        out.println("YES");
    }

    FastScanner in;
    PrintWriter out;

    void run() throws IOException {
        boolean oj;
        try {
            oj = ! System.getProperty("user.dir").equals("F:\\java_workspace\\leetcode");
        } catch (Exception e) {
            oj = System.getProperty("ONLINE_JUDGE") != null;
        }

        InputStream is = oj ? System.in : new FileInputStream(new File(INPUT));
        in = new FastScanner(is);
        out = new PrintWriter(System.out);
        long s = System.currentTimeMillis();
        read();
        out.flush();
        if (!oj){
            System.out.println("[" + (System.currentTimeMillis() - s) + "ms]");
        }
    }

    public boolean more(){
        return in.hasNext();
    }

    public int ni(){
        return in.nextInt();
    }

    public long nl(){
        return in.nextLong();
    }

    public double nd(){
        return in.nextDouble();
    }

    public String ns(){
        return in.nextString();
    }

    public char nc(){
        return in.nextChar();
    }

    class FastScanner {
        BufferedReader br;
        StringTokenizer st;
        boolean hasNext;

        public FastScanner(InputStream is) throws IOException {
            br = new BufferedReader(new InputStreamReader(is));
            hasNext = true;
        }

        public String nextToken() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (Exception e) {
                    hasNext = false;
                    return "##";
                }
            }
            return st.nextToken();
        }

        String next = null;
        public boolean hasNext(){
            next = nextToken();
            return hasNext;
        }

        public int nextInt() {
            if (next == null){
                hasNext();
            }
            String more = next;
            next = null;
            return Integer.parseInt(more);
        }

        public long nextLong() {
            if (next == null){
                hasNext();
            }
            String more = next;
            next = null;
            return Long.parseLong(more);
        }

        public double nextDouble() {
            if (next == null){
                hasNext();
            }
            String more = next;
            next = null;
            return Double.parseDouble(more);
        }

        public String nextString(){
            if (next == null){
                hasNext();
            }
            String more = next;
            next = null;
            return more;
        }

        public char nextChar(){
            if (next == null){
                hasNext();
            }
            String more = next;
            next = null;
            return more.charAt(0);
        }
    }
}