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Commit c3c74d5

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20200905
1 parent ea21740 commit c3c74d5

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3 files changed

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3 files changed

+115
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/*
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* @lc app=leetcode id=1305 lang=java
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*
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* [1305] All Elements in Two Binary Search Trees
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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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*/
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class Solution {
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/*
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Two stack and merge sort
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time: O(n)
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space: O(h)
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*/
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public List<Integer> getAllElements(TreeNode root1, TreeNode root2) {
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List<Integer> res = new ArrayList<>();
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Stack<TreeNode> s1 = new Stack<>();
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Stack<TreeNode> s2 = new Stack<>();
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pushLeft(s1, root1);
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pushLeft(s2, root2);
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while (!s1.isEmpty() || !s2.isEmpty()) {
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Stack<TreeNode> cur;
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if (s1.isEmpty()) cur = s2;
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else if (s2.isEmpty()) cur = s1;
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else {
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cur = s1.peek().val < s2.peek().val ? s1 : s2;
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}
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TreeNode node = cur.pop();
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res.add(node.val);
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pushLeft(cur, node.right);
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}
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return res;
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}
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private void pushLeft(Stack<TreeNode> stack, TreeNode root) {
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while (root != null) {
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stack.push(root);
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root = root.left;
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}
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}
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}
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// @lc code=end
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‎Java/198.house-robber.java

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/*
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* @lc app=leetcode id=198 lang=java
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*
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* [198] House Robber
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*/
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// @lc code=start
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class Solution {
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/*
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prevMax记录前一家没有抢的max, curMax记录当前家一定抢的max
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time: O(n)
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space: O(1)
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*/
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public int rob(int[] nums) {
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if (nums == null || nums.length == 0) return 0;
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int prevMax = 0, curMax = 0;
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for (int num : nums) {
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int temp = curMax;
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curMax = Math.max(curMax, prevMax + num);
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prevMax = temp;
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}
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return curMax;
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}
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}
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// @lc code=end
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‎Java/213.house-robber-ii.java

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/*
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* @lc app=leetcode id=213 lang=java
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*
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* [213] House Robber II
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*/
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// @lc code=start
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class Solution {
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/*
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分第一家抢or not两种情况取dp最大值
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time: O(n)
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space: O(1)
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*/
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public int rob(int[] nums) {
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if (nums == null || nums.length == 0) return 0;
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if (nums.length == 1) return nums[0];
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return Math.max(helper(nums, 0, nums.length - 2), helper(nums, 1, nums.length - 1));
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}
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private int helper(int[] nums, int start, int end) {
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int prevMax = 0, curMax = 0;
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for (int i = start; i <= end; ++i) {
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int temp = curMax;
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curMax = Math.max(curMax, prevMax + nums[i]);
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prevMax = temp;
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}
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return curMax;
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}
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}
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// @lc code=end
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