/**
* @see IOI2009国家集训队论文《后缀数组——处理字符串的有力工具》
* @author leon
*
*/
public class SuffixArray {
int max_char = '\uffff';
char separator = '$';
char eof = '#';
int[][] rmq;
String text = "";
int min_len = Integer.MAX_VALUE;
int lcs = 0;
int index = -1;
private void countingSort(Struct[] in, Struct[] out, int max, int compare_index) {
int[] temp = new int[max + 1];
for (int i = 0; i < in.length; i++) {
temp[in[i].compareAry[compare_index]]++;
}
for (int i = 1; i < temp.length; i++) {
temp[i] += temp[i - 1];
}
for (int i = in.length - 1; i >= 0; i--) {
out[--temp[in[i].compareAry[compare_index]]] = in[i];
}
}
/**
* Doubling Algorithm
*
* @param text
* @return
*/
public Suffix buildSuffixArray(String text) {
Struct[] in = new Struct[text.length()];
for (int i = 0; i < in.length; i++) {
in[i] = new Struct(i, new int[] { 0, text.charAt(i) });
}
Struct[] aux = (Struct[]) in.clone();
countingSort(aux, in, max_char, 1);
int[] rank = new int[in.length];
int len = text.length();
int wid = 1;
Struct[] temp = new Struct[len];
while (wid < len) {
rank[in[0].suffix_i] = 0;
for (int i = 1; i < len; i++) {
rank[in[i].suffix_i] = rank[in[i - 1].suffix_i];
if (in[i - 1].compareTo(in[i]) < 0) {
rank[in[i].suffix_i]++;
}
}
for (int i = 0; i < len; i++) {
in[i].suffix_i = i;
in[i].compareAry[0] = rank[i];
in[i].compareAry[1] = i + wid < len ? rank[i + wid] : 0;
}
countingSort(in, temp, len, 1);
countingSort(temp, in, len, 0);
wid *= 2;
}
int[] sa = new int[rank.length];
for (int i = 0; i < rank.length; i++) {
sa[rank[i]] = i;
}
Suffix rs = new Suffix();
rs.text = text;
rs.rank = rank;
rs.sa = sa;
rs.h = calH(rank, sa, text.toCharArray());
rs.height = calHeight(rs.h, sa);
return rs;
}
private int[] calHeight(int[] h, int[] sa) {
int[] height = new int[h.length];
for (int i = 0; i < height.length; i++) {
height[i] = h[sa[i]];
}
return height;
}
private int[] calH(int[] rank, int[] sa, char[] text) {
int[] h = new int[rank.length];
if (rank[0] == 0) {
h[0] = 0;
} else {
h[0] = getH(text, 0, sa[rank[0] - 1]);
}
for (int i = 1; i < h.length; i++) {
if (rank[i] == 0) {
h[i] = 0;
} else {
if (h[i - 1] <= 1) {
h[i] = getH(text, i, sa[rank[i] - 1]);
} else {
h[i] = h[i - 1] - 1 + getH(text, i + h[i - 1] - 1, sa[rank[i] - 1] + h[i - 1] - 1);
}
}
}
return h;
}
private int getH(char[] text, int i, int j) {
int len = 0;
while (i < text.length && j < text.length) {
if (text[i] == text[j] && text[i] != separator && text[j] != separator) {
i++;
j++;
len++;
} else {
break;
}
}
return len;
}
public int inquireRMQ(int u, int v, int[] height) {
if (u > v) {
int temp = u;
u = v;
v = temp;
}
if (u == v)
return height[u];
int k = (int) (Math.log(1.0 * (v - u + 1)) / Math.log(2.0));
if (rmq[u][k] < rmq[v - (1 << k) + 1][k])
return rmq[u][k];
else
return rmq[v - (1 << k) + 1][k];
}
public void buildRMQ(int[] height) {
int n = height.length;
rmq = new int[n][n];
for (int i = 1; i < height.length; i++)
rmq[i][0] = height[i];
for (int j = 1; (1 << j) < n; j++) {
for (int i = 1; i < n; i++) {
rmq[i][j] = rmq[i][j - 1];
if (i + (1 << (j - 1)) < n) {
if (rmq[i][j] > rmq[i + (1 << (j - 1))][j - 1]) {
rmq[i][j] = rmq[i + (1 << (j - 1))][j - 1];
}
}
}
}
}
private int[] getRange(String[] texts) {
int len = 0;
for (int i = 0; i < texts.length; i++) {
if (min_len > texts[i].length()) {
min_len = texts[i].length();
}
text += texts[i];
text += separator;
}
text += eof;
len = text.length();
int[] ary = new int[len];
int j = 0;
int k = 0;
for (int i = 0; i < texts.length; i++) {
int offset = texts[i].length() + 1;
k += offset;
while (j < k) {
ary[j] = i;
j++;
}
}
return ary;
}
private void binarySearch(int[] height, int[] sa, int[] range, int n) {
int low = 0;
int high = min_len;
while (low <= high) {
int mid = (low + high) >> 1;
if (checkMid(mid, height, sa, range, n)) {
low = mid + 1;
} else {
high = mid - 1;
}
}
}
private boolean checkMid(int mid, int[] height, int[] sa, int[] range, int n) {
for (int i = 2; i < height.length; i++) {
for (int j = i + n - 2; j < height.length; j++) {
if (inquireRMQ(i, j, height) >= mid) {
int sa_from = i - 1;
int sa_to = j;
if (inRange(range, sa, sa_from, sa_to, n)) {
lcs = mid;
index = sa[sa_from];
return true;
}
} else {
break;
}
}
}
return false;
}
private boolean checkMid_old(int mid, int[] height, int[] sa, int[] range, int n) {
int count = 1;
for (int i = 2; i < height.length; i++) {
int j = i;
while (j < height.length && height[j] >= mid) {
count++;
j++;
}
if (count < n) {
count = 1;
} else {
int sa_from = i - 1;
int sa_to = j;
if (inRange(range, sa, sa_from, sa_to, n)) {
lcs = mid;
index = sa[sa_from];
return true;
}
count = 1;
}
}
return false;
}
public String lcs(String[] texts) {
int[] range = getRange(texts);
Suffix suffix = buildSuffixArray(text);
buildRMQ(suffix.height);
binarySearch(suffix.height, suffix.sa, range, texts.length);
if (lcs == 0) {
return "EOF";
}
return text.substring(index, index + lcs);
}
public boolean inRange(int[] range, int[] sa, int sa_from, int sa_to, int n) {
boolean[] visit = new boolean[n];
int count = 0;
for (int i = sa_from; i <= sa_to; i++) {
if (!visit[range[sa[i]]]) {
visit[range[sa[i]]] = true;
count++;
}
}
if (count == n) {
return true;
}
return false;
}
public static void main(String[] args) {
SuffixArray sa = new SuffixArray();
String s = sa.lcs(new String[] { "adcccbadbbcadcccbba", "aabbccaacccabcca", "abccabccaccc", "e" });
System.out.println(s);
}
}
class Suffix {
public String text;
public int[] rank;
public int[] sa;
public int[] h;
public int[] height;
}
class Struct implements Comparable<Struct> {
public int suffix_i;
public int[] compareAry = new int[2];
public Struct(int suffix_i, int[] compareAry) {
this.suffix_i = suffix_i;
this.compareAry = compareAry;
}
public int compareTo(Struct st) {
Struct other = st;
int key0 = this.compareAry[0];
int key1 = this.compareAry[1];
int s0 = other.compareAry[0];
int s1 = other.compareAry[1];
if (key0 < s0) {
return -1;
} else if (key0 == s0) {
return (key1 < s1 ? -1 : (key1 == s1 ? 0 : 1));
} else {
return 1;
}
}
public String toString() {
return "suffix(i)=" + this.suffix_i + ":" + compareAry[0] + "," + compareAry[1];
}
}
