挑战程序竞赛系列（67）：4.7字符串匹配（2）

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挑战程序竞赛系列（67）：4.7字符串匹配（2）

传送门：Codeforces 25E: Test

题意：

出题：众所周知，程序竞赛测试数据越变态越好玩。已知3个字符串会使选手的程序出错，出题者想构造一个超级变态数据同时包含这3个字符串。求该母串最小长度。

依旧是滚动hash，如书上的解释：
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采用了LONG 64位无符号hash映射，此处之所以比传统的overlap算法快，是因为hash算法能够在O(1)的时间内，得到两个比较区间的hash值。

hs[i] : c[1] * B^(i - 1) + c[2] * B^(i - 2) + ... + c[i] * B^0hs[e] : c[1] * B^(e - 1) + c[2] * B^(e - 2) + ... + c[e] * B^0hs[b] : c[1] * B^(b - 1) + c[2] * B^(b - 2) + ... + c[b] * B^0任意某个区间的hash值为：c[b+1] * B^(e - b - 1) + c[b+2] * B^(e - b - 2) + ... + c[e] * B^0所以：上述表达式 = hs[e] - hs[b] * B^(e - b);

代码如下：

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.Arrays;import java.util.Random;import java.util.StringTokenizer;public class Main {    String INPUT = "./data/judge/201709/C025E.txt";    public static void main(String[] args) throws IOException {        new Main().run();    }    static final int[][] CIR = {{0, 1, 2},{0, 2, 1},{1, 0, 2},{1, 2, 0},{2, 0, 1},{2, 1, 0}};    static final int INF = 0x3f3f3f3f;    class Hash{        final long BL;        final long BR;        final long ML;        final long MR;        final long[] psl;        final long[] psr;        Hash(int n){            Random r = new Random(System.nanoTime());            BL = (long) (1e9 + r.nextInt((int)(1e9)));            BR = (long) (1e9 + r.nextInt((int)(1e9)));            ML = (long) (1e9 + r.nextInt((int)(1e9)));            MR = (long) (1e9 + r.nextInt((int)(1e9)));            psl = new long[n + 1];            psr = new long[n + 1];            for (int i = 0; i <= n; ++i) psl[i] = (i == 0 ? 1 : psl[i - 1] * BL) % ML;            for (int i = 0; i <= n; ++i) psr[i] = (i == 0 ? 1 : psr[i - 1] * BR) % MR;        }        long[] build(char[] cs) {            int n = cs.length;            long[] hs = new long[n + 1];            long l = 0;            long r = 0;            for (int i = 0; i < n; ++i) {                l = (l * BL + cs[i]) % ML;                r = (r * BR + cs[i]) % MR;                if (l < 0) l += ML;                if (r < 0) r += MR;                hs[i + 1] = l << 32 | r;            }            return hs;        }        long get(long[] hs, int b, int e) {            long el = hs[e] >>> 32;            long er = hs[e] & 0xffffffffL;            long bl = hs[b] >>> 32;            long br = hs[b] & 0xffffffffL;            long l = el - bl * psl[e - b] % ML;            long r = er - br * psr[e - b] % MR;            if (l < 0) l += ML;            if (r < 0) r += MR;            return l << 32 | r;        }    }    int overlap(long[] ah, long[] bh, int al, int bl, Hash h) {        int l = -1;        for (int i = 0; i <= Math.min(al, bl); ++i) {            if (h.get(ah, al - i, al) == h.get(bh, 0, i)) l = i;        }        return l == -1 ? 0 : l;    }    // al > bl    boolean contains(long[] ah, long[] bh, int al, int bl, Hash h) {        if (al < bl) return false;        long key = h.get(bh, 0, bl);        for (int i = bl; i <= al; ++i) {            if (key == h.get(ah, i - bl, i)) return true;        }        return false;    }    int solveContains(long[] ah, long[] bh, long ch[], int al, int bl, int cl, Hash hash) {        if (contains(ah, bh, al, bl, hash) && contains(bh, ch, bl, cl, hash)) {            return al;        }        else if (contains(ah, bh, al, bl, hash)) {            return Math.min(al + cl -  overlap(ah, ch, al, cl, hash),                    al + cl - overlap(ch, ah, cl, al, hash));        }        return INF;    }    class Pair{        int len;        long[] hs;        Pair(int len, long[] hs){            this.len = len;            this.hs  = hs;        }    }    int solve(String s1, String s2, String s3) {        int al = s1.length();        int bl = s2.length();        int cl = s3.length();        Hash hash = new Hash(Math.max(al, Math.max(bl, cl)));        long[] ah = hash.build(s1.toCharArray());        long[] bh = hash.build(s2.toCharArray());        long[] ch = hash.build(s3.toCharArray());        Pair[] p = new Pair[3];        p[0] = new Pair(al, ah);        p[1] = new Pair(bl, bh);        p[2] = new Pair(cl, ch);        int min = INF;        for (int i = 0; i < CIR.length; ++i) {            min = Math.min(min, solveContains(p[CIR[i][0]].hs, p[CIR[i][1]].hs, p[CIR[i][2]].hs,                     p[CIR[i][0]].len, p[CIR[i][1]].len, p[CIR[i][2]].len, hash));        }        for (int i = 0; i < CIR.length; ++i) {            int ans = al + bl + cl;            ans -= overlap(p[CIR[i][0]].hs, p[CIR[i][1]].hs, p[CIR[i][0]].len, p[CIR[i][1]].len, hash);            ans -= overlap(p[CIR[i][1]].hs, p[CIR[i][2]].hs, p[CIR[i][1]].len, p[CIR[i][2]].len, hash);            min = Math.min(min, ans);        }        return min;    }    void read() {        String s1 = ns();        String s2 = ns();        String s3 = ns();        out.println(solve(s1, s2, s3));    }    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);        }    }    static class ArrayUtils {        public static void fill(int[][] f, int value) {            for (int i = 0; i < f.length; ++i) {                Arrays.fill(f[i], value);            }        }        public static void fill(int[][][] f, int value) {            for (int i = 0; i < f.length; ++i) {                fill(f[i], value);            }        }        public static void fill(int[][][][] f, int value) {            for (int i = 0; i < f.length; ++i) {                fill(f[i], value);            }        }    }}

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