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PalindromicTree.java
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PalindromicTree.java
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package com.algorithm.playground.data.structure;
import java.util.*;
public class PalindromicTree {
private final PalindromicNode[] tree;
private final char[] value;
private final int max;
public PalindromicTree(String s) {
this(s.toCharArray());
}
public PalindromicTree(char[] chars) {
this.value = chars;
Tuple2<PalindromicNode[], Integer> tuple = new PalindromicTreeBuilder().build();
this.tree = tuple._1();
this.max = tuple._2();
}
public String getMaxPalindrome() {
if (tree[max].getLength() < 0) {
return "";
}
return new String(value, tree[max].start, tree[max].getLength());
}
public List<String> getAllPalindrome() {
List<String> list = new ArrayList<>();
for (int i = 2; i < tree.length; i++) {
list.add(new String(value, tree[i].start, tree[i].getLength()));
}
return list;
}
@Override
public String toString() {
StringBuilder builder = new StringBuilder();
int len = countDigits(tree.length);
for (int i = 0; i < tree.length; i++) {
builder.append("\t\t")
.append(padding(i, len))
.append(" : ")
.append(tree[i])
.append('\n');
}
return "PalindromicTree{\n" +
"\tvalue = '" + new String(value) +
"'\n\ttree : \n" + builder +
'}';
}
private String padding(int i, int len) {
len = len - countDigits(i);
StringBuilder builder = new StringBuilder();
for (int j = 0; j < len; j++) {
builder.append(' ');
}
return builder.append(i).toString();
}
private int countDigits(int i) {
int count = i == 0 ? 1 : 0;
//noinspection StatementWithEmptyBody
for (; i > 0; count++, i /= 10) ;
return count;
}
private class PalindromicTreeBuilder {
private final PalindromicNode[] tree;
private int current;
private int pointer;
private int max;
private PalindromicTreeBuilder() {
this.tree = new PalindromicNode[value.length + 2];
this.pointer = 2;
}
private Tuple2<PalindromicNode[], Integer> build() {
tree[0] = new PalindromicNode(0, -2, 0);
tree[1] = new PalindromicNode(0, -1, 0);
for (int i = 0; i < value.length; i++) {
int palindrome = getPalindrome(current, i);
createIfNotExist(palindrome, i);
}
return new Tuple2<>(Arrays.copyOf(tree, pointer), max);
}
private void createIfNotExist(int node, int idx) {
char ch = value[idx];
Integer child = tree[node].edges.putIfAbsent(ch, pointer);
if (child == null) {
tree[pointer] = new PalindromicNode(idx - tree[node].getLength() - 1, idx);
if (tree[pointer].getLength() == 1) {
tree[pointer].maxPalindromicEdge = 1;
} else {
int edge = tree[node].maxPalindromicEdge;
int palindrome = getPalindrome(edge, idx);
tree[pointer].maxPalindromicEdge = tree[palindrome].edges.get(ch);
}
current = pointer++;
} else {
current = child;
}
if (tree[current].getLength() > tree[max].getLength()) {
max = current;
}
}
private int getPalindrome(int node, int idx) {
while (true) {
int curr = tree[node].getLength();
if (idx - curr > 0 && value[idx] == value[idx - curr - 1]) {
return node;
}
node = tree[node].maxPalindromicEdge;
}
}
}
private class PalindromicNode {
private int start, end;
private Map<Character, Integer> edges = new HashMap<>();
private int maxPalindromicEdge;
private PalindromicNode(int start, int end, int maxPalindromicEdge) {
this(start, end);
this.maxPalindromicEdge = maxPalindromicEdge;
}
private PalindromicNode(int start, int end) {
this.start = start;
this.end = end;
}
private int getLength() {
return end - start + 1;
}
@Override
public String toString() {
return "PalindromicNode{" +
"start=" + start +
", end=" + end +
", maxPalindromicEdge=" + maxPalindromicEdge +
", edges=" + edges +
'}';
}
}
}