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. Ensure that numbers within the set are sorted in ascending order. Example 1…

Given a 2d grid map of '1's (land) and '0's (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may assume all four edges of the grid are all surrounded by…

1. Description The thief has found himself a new place for his thievery again. There is only one entrance to this area, called the "root." Besides the root, each house has one and only one parent house. After a tour, the smart thief realized tha…

Sort a linked list using insertion sort. 思路: 用插入排序对链表排序.插入排序是指每次在一个排好序的链表中插入一个新的值. 注意:把排好序的部分和未排序的部分完全分开,指针不要有交叉. 即不会通过->next 重叠 class Solution { public: ListNode *insertionSortList(ListNode *head) { if(head == NULL) return NULL; ListNode * ans = hea…

All DNA is composed of a series of nucleotides abbreviated as A, C, G, and T, for example: "ACGAATTCCG". When studying DNA, it is sometimes useful to identify repeated sequences within the DNA. Write a function to find all the 10-letter-long seq…

Given a binary tree, determine if it is height-balanced. For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1. 思路: 我居然在这道题上卡了一个小时.关键是对于平衡的定义,我开始理解…

Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place. 思路:不能用额外空间,就用矩阵的第一行和第一列来标记这一行或这一列是否需要置0. 用两个bool量记录第一行和第一列是否需要置0 大神的代码和我的代码都是这个思路,但是我在画0的时候是行列分开处理的,大神的代码是一起处理的 void setZeroes(vector<vector<int> > &…

Given an integer n, generate a square matrix filled with elements from 1 to n2 in spiral order. For example,Given n = 3, You should return the following matrix: [ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ] ] 思路: 我是直接套用了Spiral Matrix 的代码 class Solution { p…

Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order. You may assume no duplicates in the array. Here are few examples.[1,3,5,6], 5 → 2[1,3,5,6], 2 →…

Compare two version numbers version1 and version2.If version1 > version2 return 1, if version1 < version2 return -1, otherwise return 0. You may assume that the version strings are non-empty and contain only digits and the . character.The . characte…