Description Reverse digits of an integer. Returns 0 when the reversed integer overflows (signed 32-bit integer). Example Given x = 123, return 321 Given x = -123, return -321 解题:注意别溢出即可,所以结果用long型变量保存,最后返回的时候强转成int型.代码如下: public class Solution { /**…

Reverse digits of an integer. Returns 0 when the reversed integer overflows (signed 32-bit integer).   Example Given x = 123, return 321 Given x = -123, return -321 解法一: class Solution { public: /* * @param n: the integer to be reversed * @return: th…

1.在进入while之前,保证x是非负的: 2.符号还是专门用flag保存 =================== 3.另一思路:将integer转换成string,然后首位swap,直至中间: class Solution: # @return an integer def reverse(self, x): ret = 0 flag = 1 if x < 0: flag = -1 x *= -1 while(x!=0): ret = ret*10+x%10 x = x/10 return r…

Description Cosine similarity is a measure of similarity between two vectors of an inner product space that measures the cosine of the angle between them. The cosine of 0° is 1, and it is less than 1 for any other angle. See wiki: Cosine Similarity H…

Description Given a boolean 2D matrix, 0 is represented as the sea, 1 is represented as the island. If two 1 is adjacent, we consider them in the same island. We only consider up/down/left/right adjacent. Find the number of islands. Example Given gra…

Description The count-and-say sequence is the sequence of integers beginning as follows: 1, 11, 21, 1211, 111221, ... 1 is read off as "one 1" or 11. 11 is read off as "two 1s" or 21. 21 is read off as "one 2, then one 1" or …

Description Given two binary strings, return their sum (also a binary string). Example a = 11 b = 1 Return 100 解题:二进制相加.我的思路是,先转成StringBuilder对象(reverse方法比较好用),因为相加是从最后开始,所以先用reverse方法倒转过来.和上一题类似,用carry变量表示进位,0为不进位,1为需要进一位.最后的结果再倒过来.具体细节标注在代码中,代码如下:…

Description Given a binary tree, find all paths that sum of the nodes in the path equals to a given number target. A valid path is from root node to any of the leaf nodes. Example Given a binary tree, and target = 5: 1 / \ 2 4 / \ 2 3 return [ [1, 2,…

Description Implement an algorithm to delete a node in the middle of a singly linked list, given only access to that node. Example Linked list is 1->2->3->4, and given node 3, delete the node in place 1->2->4 解题:删除指定的结点.由于java没有delete 或者 fr…

Description Count how many 1 in binary representation of a 32-bit integer. Example Given 32, return 1 Given 5, return 2 Given 1023, return 9 Challenge If the integer is n bits with m 1 bits. Can you do it in O(m) time? 解题:很简单,但是要考虑范围的问题.代码如下: public…