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Commit 624b130

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20200825
1 parent d1afef3 commit 624b130

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5 files changed

+213
-0
lines changed

5 files changed

+213
-0
lines changed

‎Java/1032.stream-of-characters.java‎

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/*
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* @lc app=leetcode id=1032 lang=java
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*
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* [1032] Stream of Characters
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*/
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// @lc code=start
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/*
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将dict中的单词逆序存入一个trie中,query的时候倒序在trie中搜索
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time: O(n * m) n: number of words m: length of word
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space: O(n * m)
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*/
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class StreamChecker {
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class TrieNode {
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TrieNode[] children;
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boolean isWord;
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public TrieNode() {
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children = new TrieNode[26];
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isWord = false;
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}
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}
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TrieNode root;
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StringBuilder sb;
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public StreamChecker(String[] words) {
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root = new TrieNode();
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buildTrie(words);
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sb = new StringBuilder();
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}
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public boolean query(char letter) {
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sb.append(letter);
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TrieNode cur = root;
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for (int i = sb.length() - 1; i >= 0 && cur != null; --i) {
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cur = cur.children[sb.charAt(i) - 'a'];
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if (cur != null && cur.isWord) {
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return true;
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}
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}
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return false;
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}
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private void buildTrie(String[] words) {
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for (String word : words) {
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TrieNode cur = root;
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// build Trie in reverse order
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for (int i = word.length() - 1; i >= 0; --i) {
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if (cur.children[word.charAt(i) - 'a'] == null) {
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cur.children[word.charAt(i) - 'a'] = new TrieNode();
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}
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cur = cur.children[word.charAt(i) - 'a'];
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}
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cur.isWord = true;
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}
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}
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}
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/**
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* Your StreamChecker object will be instantiated and called as such:
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* StreamChecker obj = new StreamChecker(words);
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* boolean param_1 = obj.query(letter);
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*/
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// @lc code=end
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‎Java/143.reorder-list.java‎

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/*
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* @lc app=leetcode id=143 lang=java
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*
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* [143] Reorder List
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*/
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// @lc code=start
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/**
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* Definition for singly-linked list.
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* public class ListNode {
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* int val;
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* ListNode next;
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* ListNode() {}
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* ListNode(int val) { this.val = val; }
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* ListNode(int val, ListNode next) { this.val = val; this.next = next; }
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* }
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*/
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class Solution {
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/*
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将链表对半分,reverse后一半,再merge list]
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time: O(n)
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space: O(1)
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*/
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public void reorderList(ListNode head) {
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if (head == null || head.next == null) return;
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ListNode slow = head;
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ListNode fast = slow.next;
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while (fast != null && fast.next != null) {
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slow = slow.next;
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fast = fast.next.next;
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}
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ListNode p = slow.next;
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slow.next = null;
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p = reverse(p);
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ListNode cur = head;
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while (p != null) {
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ListNode temp = cur.next;
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ListNode nextP = p.next;
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cur.next = p;
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p.next = temp;
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cur = temp;
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p = nextP;
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}
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}
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private ListNode reverse(ListNode head) {
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ListNode dummy = new ListNode(0);
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while (head != null) {
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ListNode temp = head.next;
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ListNode tempNext = dummy.next;
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dummy.next = head;
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head.next = tempNext;
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head = temp;
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}
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return dummy.next;
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}
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}
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// @lc code=end
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‎Java/404.sum-of-left-leaves.java‎

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/*
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* @lc app=leetcode id=404 lang=java
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*
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* [404] Sum of Left Leaves
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*/
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// @lc code=start
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/**
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* Definition for a binary tree node.
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* public class TreeNode {
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* int val;
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* TreeNode left;
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* TreeNode right;
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* TreeNode() {}
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* TreeNode(int val) { this.val = val; }
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* TreeNode(int val, TreeNode left, TreeNode right) {
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* this.val = val;
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* this.left = left;
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* this.right = right;
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* }
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* }
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*/
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class Solution {
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public int sumOfLeftLeaves(TreeNode root) {
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if (root == null) return 0;
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int res = 0;
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if (root.left != null) {
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if (root.left.left == null && root.left.right == null) {
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res += root.left.val;
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} else {
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res += sumOfLeftLeaves(root.left);
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}
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}
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res += sumOfLeftLeaves(root.right);
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return res;
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}
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}
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// @lc code=end
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‎Java/905.sort-array-by-parity.java‎

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/*
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* @lc app=leetcode id=905 lang=java
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*
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* [905] Sort Array By Parity
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*/
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// @lc code=start
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class Solution {
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public int[] sortArrayByParity(int[] A) {
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int i = 0, j = A.length - 1;
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while (i < j) {
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if ((A[i] % 2 == 1) && (A[j] % 2 == 0)) {
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int temp = A[i];
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A[i] = A[j];
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A[j] = temp;
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}
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if (A[i] % 2 == 0) i++;
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if (A[j] % 2 == 1) j--;
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}
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return A;
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}
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}
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// @lc code=end
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/*
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* @lc app=leetcode id=983 lang=java
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*
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* [983] Minimum Cost For Tickets
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*/
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// @lc code=start
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class Solution {
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public int mincostTickets(int[] days, int[] costs) {
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Set<Integer> set = new HashSet<>();
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for (int day : days) {
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set.add(day);
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}
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int[] dp = new int[366];
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for (int i = 1; i <= 365; ++i) {
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if (!set.contains(i)) dp[i] = dp[i - 1];
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else {
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dp[i] = Math.min(dp[i - 1] + costs[0], Math.min(dp[Math.max(0, i - 7)] + costs[1], dp[Math.max(0, i - 30)] + costs[2]));
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}
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}
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return dp[365];
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}
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}
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// @lc code=end
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