挑战程序竞赛系列（73）：4.7高度数组（3）

挑战程序竞赛系列（73）：4.7高度数组（3）

传送门：POJ 3729: Facer’s String

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题意：

公共子串：
给出两个字符串A,B,求满足下列条件的C的个数:
1. C是A的子串
2. C也是B的子串
3. C加上其在A中的后继字符(若在最尾则加上空格字符)不能够在B中出现

其实就是问A中有多少个长度为K的子串在B中刚好存在,且再加上后一个字符形成的子串在B中不存在.

思路：
求出A中存在多少后缀，使得其和B的前缀长度大于等于k，再求出A中存在多少后缀，使得其和B的前缀长度等于k+1，最后两式相减。

所以在>=k的范围内，存在一个B，就可以统计A的后缀个数了，若没有B，则统计也没用。

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.Comparator;import java.util.Map;import java.util.StringTokenizer;public class Main{    String INPUT = "./data/judge/201709/P3729.txt";    public static void main(String[] args) throws IOException {        new Main().run();    }    class SuffixArray {        int k = 1;        int n;        Integer[] sa;        int[] rank, tmp;        int[] lcp;        SuffixArray(int[] arra) {            n = arra.length;            sa = new Integer[n + 1];            rank = new int[n + 1];            tmp = new int[n + 1];            lcp = new int[n];            for (int i = 0; i <= n; ++i) {                sa[i] = i;                rank[i] = i < n ? arra[i] : -1;            }            for (k = 1; k <= n; k <<= 1) {                Arrays.sort(sa, cmp);                tmp[sa[0]] = 0;                for (int i = 1; i <= n; ++i) {                    tmp[sa[i]] = tmp[sa[i - 1]] + (cmp.compare(sa[i - 1], sa[i]) < 0 ? 1 : 0);                }                for (int i = 0; i <= n; ++i) {                    rank[i] = tmp[i];                }            }            // lcp            int h = 0;            for (int i = 0; i <= n; ++i)                rank[sa[i]] = i;            for (int i = 0; i < n; ++i) {                int j = sa[rank[i] - 1];                if (h > 0)                    h--;                for (; i + h < n && j + h < n; ++h) {                    if (arra[i + h] != arra[j + h])                        break;                }                lcp[rank[i] - 1] = h;            }        }        Comparator<Integer> cmp = new Comparator<Integer>() {            @Override            public int compare(Integer o1, Integer o2) {                int i = o1;                int j = o2;                if (rank[i] != rank[j])                    return rank[i] - rank[j];                else {                    int ri = i + k <= n ? rank[i + k] : -1;                    int rj = j + k <= n ? rank[j + k] : -1;                    return ri - rj;                }            }        };    }    void read() {        while (more()) {            int m = ni();            int n = ni();            int k = ni();            int[] arra = new int[m + n + 1];            for (int i = 0; i < m; ++i) {                arra[i] = ni();                arra[i] ++;            }            arra[m] = 10000 + 8;            for (int i = 0; i < n; ++i) {                arra[i + m + 1] = ni();                arra[i + m + 1] ++;            }            SuffixArray sa = new SuffixArray(arra);            out.println(solve(k, m, sa) - solve(k + 1, m, sa));        }    }    int solve(int k, int m, SuffixArray sa) {        int ans = 0, A = 0, B = 0;        for (int i = 0; i < sa.n; i++) {// 统计lcp[i]>=k的连续区间内的A子串            if (sa.lcp[i] < k) {                if (B > 0)                    ans += A;                A = 0;                B = 0;            }            if (sa.sa[i + 1] < m)                A++;            else                B++;        }        return ans;    }    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);            }        }    }}