==============================  2的幂次  ================================  最佳解法 如果一个数是2的次方数的话,根据上面分析,那么它的二进数必然是最高位为1,其它都为0,那么如果此时我们减1的话,则最高位会降一位,其余为0的位现在都为变为1,那么我们把两数相与,就会得到0,用这个性质也能来解题,而且只需一行代码就可以搞定,如下所示: class Solution { public: bool isPowerOfTwo(int…

142. O(1) Check Power of 2[easy] Using O(1) time to check whether an integer n is a power of 2. Have you met this question in a real interview? Yes Example For n=4, return true; For n=5, return false; Challenge O(1) time 解法一: class Solution { public:…

[SPOJ]Power Modulo Inverted(拓展BSGS) 题面 洛谷 求最小的\(y\) 满足 \[k\equiv x^y(mod\ z)\] 题解 拓展\(BSGS\)模板题 #include<iostream> #include<cstdio> #include<cstdlib> #include<cstring> #include<cmath> #include<algorithm> #include<set…

[CF913G]Power Substring 题意:T组询问,每次给定一个数a,让你求一个k,满足$2^k$的10进制的后$min(100,length(k))$位包含a作为它的子串.你只需要输出一个k,不需要最小化k的值,保证有解. $T\le 2000,a\le 10^{11}$ 题解:神题. 假设a有n位,$2^k=x$,$x=a\times 10^m+b(\mod 10^{n+m})$,我们显然有$k\ge n+m$,所以$2^{n+m}\mid x$,又因为$2^{n+m}\mid…

170. Two Sum III - Data structure design[easy] Design and implement a TwoSum class. It should support the following operations:add and find. add - Add the number to an internal data structure.find - Find if there exists any pair of numbers which sum…

160. Intersection of Two Linked Lists[easy] Write a program to find the node at which the intersection of two singly linked lists begins. For example, the following two linked lists: A: a1 → a2 ↘ c1 → c2 → c3 ↗ B: b1 → b2 → b3 begin to intersect at n…

206. Reverse Linked List[easy] Reverse a singly linked list. Hint: A linked list can be reversed either iteratively or recursively. Could you implement both? 解法一: class Solution { public: ListNode* reverseList(ListNode* head) { ListNode * pre = NULL;…

203. Remove Linked List Elements[easy] 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 Credits:Special than…

83. Remove Duplicates from Sorted List[easy] 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. 解法一: /** * Defin…

21. Merge Two Sorted Lists[easy] 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. 解法一: /** * Definition for singly-linked list. * struct ListNode { * int val…