挑战程序竞赛系列（71）：4.7高度数组（1）

import java.io.IOException;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Scanner;

public class Main{

    String INPUT = "./data/judge/201709/P2217.txt";

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

    void read() {
        int t = in.nextInt();
        in.nextLine();
        while (t --> 0) {
            String S = in.nextLine();
            String T = in.nextLine();
            StringBuilder sb = new StringBuilder();
            sb.append(S + '$' + T);
            SuffixArray sa = new SuffixArray(sb.toString().toCharArray());
            int max = 0;
            for (int i = 0; i < sb.length(); ++i) {
                if (sa.sa[i] < S.length() != sa.sa[i + 1] < S.length())
                    max = Math.max(max, sa.lcp[i]);
            }
            System.out.println("Nejdelsi spolecny retezec ma delku " + max + ".");
        }
    }

    class SuffixArray{
        int k = 1;
        int n;
        Integer[] sa;
        int[] rank, tmp;
        int[] lcp;

        SuffixArray(char[] cs){
            n    = cs.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 ? cs[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
            for (int i = 0; i <= n; ++i) rank[sa[i]] = i;  //求出每个后缀的当前排名
            int h = 0;
            for (int i = 0; i < n; ++i) {
                int j = sa[rank[i] - 1]; // 后缀i的前一个后缀
                if (h > 0) h--;
                for (;j + h < n && i + h < n; ++h) {
                    if (cs[j + h] != cs[i + h]) break;
                }
                lcp[rank[i] -1] = h;
            }

        }



        private 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 run() throws IOException {
        read();
    }
}