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336.java
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336.java
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__________________________________________________________________________________________________
sample 22 ms submission
class Solution {
public List<List<Integer>> palindromePairs(String[] words) {
Node root = new Node();
for (int i = 0; i < words.length; ++i) {
insert(root, i, words[i].toCharArray());
}
List<List<Integer>> result = new ArrayList<>();
for (int i = 0; i < words.length; ++i) {
search(root, i, words[i].toCharArray(), result);
}
return result;
}
static class Node {
Node[] next = new Node[26];
List<Integer> palindromTail = new ArrayList<>();
int leaf = -1;
}
private void addToResult(List<List<Integer>> result, int i, int j) {
List<Integer> pair = new ArrayList<>();
pair.add(i);
pair.add(j);
result.add(pair);
}
private void search(Node root, int num, char[] chars, List<List<Integer>> result) {
for (int i = 0; i < chars.length; ++i) {
if (root.leaf != -1 && isPalindrome(chars, i, chars.length - 1) && root.leaf != num) {
addToResult(result, num, root.leaf);
}
if (root.next[chars[i] - 'a'] == null) {
return;
}
root = root.next[chars[i] - 'a'];
}
if (root.leaf != -1 && root.leaf != num) {
addToResult(result, num, root.leaf);
}
for (int i : root.palindromTail) {
if (i != num) {
addToResult(result, num, i);
}
}
}
private void insert(Node root, int num, char[] chars) {
for (int i = chars.length - 1; i>=0; --i) {
if (isPalindrome(chars, 0, i)) {
root.palindromTail.add(num);
}
Node child = root.next[chars[i] - 'a'];
if (child == null) {
child = new Node();
root.next[chars[i] - 'a'] = child;
}
root = child;
}
//root.palindromTail.add(num);
root.leaf = num;
}
private boolean isPalindrome(char[] chars, int i, int j) {
while (i < j) {
if (chars[i] != chars[j]) {
return false;
}
++i;
--j;
}
return true;
}
}
__________________________________________________________________________________________________
sample 39780 kb submission
class Solution {
public List<List<Integer>> palindromePairs(String[] words) {
List<List<Integer>> res = new ArrayList<List<Integer>>();
for (int i = 0; i < words.length - 1; i++) {
for (int j = i + 1; j < words.length; j++) {
if (canFormPalindrome(words, i, j)) {
List<Integer> pair = new ArrayList<Integer>();
pair.add(i);
pair.add(j);
res.add(pair);
}
if (canFormPalindrome(words, j, i)) {
List<Integer> pair = new ArrayList<Integer>();
pair.add(j);
pair.add(i);
res.add(pair);
}
}
}
return res;
}
private boolean canFormPalindrome(String[] words, int i, int j) {
int shorterLength = (words[i].length() <= words[j].length()) ? words[i].length() : words[j].length();
for (int k = 0; k < shorterLength; k++) {
if (words[i].charAt(k) != words[j].charAt(words[j].length() - 1 - k)) {
return false;
}
}
if (words[i].length() <= words[j].length()) {
return isPalindrome(words[j].substring(0, words[j].length() - shorterLength));
} else {
return isPalindrome(words[i].substring(shorterLength));
}
}
private boolean isPalindrome(String word) {
int i = 0;
int j = word.length() - 1;
while (i < j) {
if (word.charAt(i) != word.charAt(j)) {
return false;
}
i += 1;
j -= 1;
}
return true;
}
}
__________________________________________________________________________________________________