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Say you have an array for which theithelement is the price of a given stock on dayi.If you were only permitted to complete at most one transaction (ie, buy one and sell one share of the stock), design an algorithm to find the maximum profit.解题思路：这个问题其实最长连续子序列和的变种。对于此题，设dp[i]为第i天卖出的最大收益，则dp[i] = max( 阅读全文
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Given an array where elements are sorted in ascending order, convert it to a height balanced BST.解题思路：递归做。/** * Definition for binary tree * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution ... 阅读全文
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iven a binary tree, return theinordertraversal of its nodes' values.For example:Given binary tree{1,#,2,3}, 1 \ 2 / 3return[1,3,2].Note:Recursive solution is trivial, could you do it iteratively?解题思路：结点的访问顺序是，左子树 -> 自己 -> 右子树。对于一个结点，它可以输出的条件是，其子树已经加入list，同时左子树已经访问完成。这里的实现和后序遍历不同，后序遍历只需... 阅读全文
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Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).For example, this binary tree is symmetric: 1 / \ 2 2 / \ / \3 4 4 3But the following is not: 1 / \ 2 2 \ \ 3 3Note:Bonus points if you could solve it both recursively and iterati... 阅读全文
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You are climbing a stair case. It takesnsteps to reach to the top.Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?解题思路：简单的递归，ways[n] = ways[n - 1] + ways[n - 2];class Solution {public: int climbStairs(int n) { // IMPORTANT: Please reset any m... 阅读全文
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Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists./** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */class So... 阅读全文
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Given two sorted integer arrays A and B, merge B into A as one sorted array.Note:You may assume that A has enough space to hold additional elements from B. The number of elements initialized in A and B aremandnrespectively.解题思路：额外开了空间，不开也可以，但是会比较麻烦。class Solution {public: void merge(int A[], int ... 阅读全文
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Find the contiguous subarray within an array (containing at least one number) which has the largest sum.For example, given the array[−2,1,−3,4,−1,2,1,−5,4],the contiguous subarray[4,−1,2,1]has the largest sum =6.click to show more practice.More practice:If you have figured out the O(n) solution, try 阅读全文
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Given a sorted array, remove the duplicates in place such that each element appear onlyonceand return the new length.Do not allocate extra space for another array, you must do this in place with constant memory.For example,Given input array A =[1,1,2],Your function should return length =2, and A is 阅读全文
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Given an array and a value, remove all instances of that value in place and return the new length.The order of elements can be changed. It doesn't matter what you leave beyond the new length.解题思路：从前往后扫一遍，遇到elem，试图从后往前找一个元素与之交换，如果找不到可以交换的元素，则停止。注意elem如果没有出现，则应该返回n。class Solution {public: int remo 阅读全文