u013546334的专栏

class HashItem{ int key, val;public: HashItem(int k, int k): key(k), val(v){} const int& getKey(){ return key; } const int& getVal(){ return val; }};...

Find all possible combinations of k numbers that add up to a number n, given that only numbers from 1 to 9 can be used and each combination should be a unique set of numbers.Example 1:Input: k = 3, n ...

Given a collection of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.Each number in C may only be used once in the combination.N...

Given a set of candidate numbers (C) (without duplicates) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.The same repeated number may be chosen from C...

Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.Examples:s = "leetcode"return 0.s = "loveleetcode",return 2.Note: You may assume...

Given a string, sort it in decreasing order based on the frequency of characters.Example 1:Input:"tree"Output:"eert"Explanation:'e' appears twice while 'r' and 't' both appear once.So 'e' must...

preorder 遍历二叉树/** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {}...

postorder遍历二叉树，参考http://blog.youkuaiyun.com/feliciafay/article/details/18341703/** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; ...

Given a string and an integer k, you need to reverse the first k characters for every 2k characters counting from the start of the string. If there are less than k characters left, reverse all of them...

判断是否为小端表示，如果是就转为大端，如果不是就直接返回。判断大小端， 存储int i为1，如果取到最后一个字节的地址，输出结果还是1，那么就是小端表示，不然就是大端表示： int i = 1; char *p = (char *)&i; if(*p == 1) printf("Little Endian"); el...

Implement atoi to convert a string to an integer.Hint: Carefully consider all possible input cases. If you want a challenge, please do not see below and ask yourself what are the possible input cases....

Given a binary search tree and a node in it, find the in-order successor of that node in the BST.Note: If the given node has no in-order successor in the tree, return null.inorder 遍历 BST 用stack模拟，先把左节...

判断一个树是不是BST因为BST是对于每一个点，左子树的所有节点都小于当前点，右子树的所有节点都大于当前点。所以其实每个子树代表一段值，可以用当前点是否超出了[min, max]范围判断是否是二叉树。 bool isBST(TreeNode* root, int min, int max) { if (root == NULL) return 1; if (root...

Remove all elements from a linked list of integers that have value val.ExampleGiven: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6Return: 1 --> 2 --> 3 --> 4 --> 5比较简单的题...

Write a function to delete a node (except the tail) in a singly linked list, given only access to that node.Supposed the linked list is 1 -> 2 -> 3 -> 4 and you are given the third node with ...

Given a binary tree, find its maximum depth.The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.For example:Given binary tree [3,9,20,null...

给你一个单链表，修改此单链表，使得前面是偶数，后面是奇数。偶数间的相对顺序不变，奇数间的相对顺序不变。返回修改后的单链表的头节点。例如：Input: 17->15->8->12->10->5->4->1->7->6->NULLOutput: 8->12->10->4->6->17->15

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.For example,Given 1->2->3->3->4->4->5, return 1->2-&...

Given a sorted linked list, delete all duplicates such that each element appear only once.For example,Given 1->1->2, return 1->2.Given 1->1->2->3->3, return 1->2->3.和26题很像，只...

Follow up for "Search in Rotated Sorted Array":What if duplicates are allowed?Would this affect the run-time complexity? How and why?Suppose an array sorted in ascending order is rotated at some pivot...

Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.(i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2).You are given a target value to search. If found in the a...

Follow up for "Remove Duplicates":What if duplicates are allowed at most twice?For example,Given sorted array nums = [1,1,1,2,2,3],Your function should return length = 5, with the first five elements ...

Find the kth largest element in an unsorted array. Note that it is the kth largest element in the sorted order, not the kth distinct element.For example,Given [3,2,1,5,6,4] and k = 2, return 5.Note: Y...

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 ...

Implement pow(x, n).Example 1:Input: 2.00000, 10Output: 1024.00000Example 2:Input: 2.10000, 3Output: 9.26100注意corner case很多，1 如果x == 1.0 或者 n == 0 应该返回12如果x= -1.0，n为偶返回1.0， n为奇数返回-1.0，必须先判断，不然n=INT...

An image is represented by a 2-D array of integers, each integer representing the pixel value of the image (from 0 to 65535).Given a coordinate (sr, sc) representing the starting pixel (row and column...

Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between tw...

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes v an...

Given a binary tree, find the length of the longest consecutive sequence path.The path refers to any sequence of nodes from some starting node to any node in the tree along the parent-child connection...

Given a sorted array, remove the duplicates in-place such that each element appear only once and return the new length.Do not allocate extra space for another array, you must do this by modifying the ...

Given a non-negative integer represented as non-empty a singly linked list of digits, plus one to the integer.You may assume the integer do not contain any leading zero, except the number 0 itself

Given an array of integers, find out whether there are two distinct indices i and j in the array such that the absolute difference between nums[i] and nums[j] is at most t and the absolute diffe

Given a string, find the length of the longest substring without repeating characters.Examples:Given "abcabcbb", the answer is "abc", which the length is 3.Given "bbbbb", the answer is "b",

这道题的类型和2.add two numbers 是一样的，只不过2的里面是2个list相加，这个是两个string相加。Given two non-negative integers num1 and num2 represented as string, return the sum of num1 and num2.Note:The length of bot

Reverse bits of a given 32 bits unsigned integer.For example, given input 43261596 (represented in binary as 00000010100101000001111010011100), return 964176192 (represented in binary as 001110010

Given an array where elements are sorted in ascending order, convert it to a height balanced BST.For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of t

There is a new alien language which uses the latin alphabet. However, the order among letters are unknown to you. You receive a list of non-empty words from the dictionary, where words are sorted le

Write an algorithm to determine if a number is "happy".A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares

不是很难的一道题，就是list操作，但是细节总是写不对。1 循环时是先while(l1 != NULL && l2 != NULL)然后在加剩下的list，但是发现这个时候也要考虑进位，所以把长list的后半段留下来并不能直接加在返回list的后面，所以还是用while(l1 != NULL || l2 != NULL)把两个list都遍历完，再处理剩下的情况，2 但是使用sum来记录总和

Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j] and the absolute difference between i and j is a