题目: You are climbing a stair case. It takes n steps 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? 代码: class Solution { public: int climbStairs(int n) { ; ; ; i<n; ++i) { const in…

题意: 给出n个地雷所在位置,正好能够组成正方形的地雷就可以拿走..为了简化题目,只考虑平行于横轴的正方形.. 问最多可以拿走多少个正方形.. 思路: 先找出可以组成正方形的地雷组合cnt个.. 然后st = 1<<cnt.. 用位运算来考虑取哪一个组合可以拿走最多的地雷且满足题目条件.. Tips: 题目比较烦恼的地方是解决: ①. 所选集合里面的地雷会不会重复拿.. ②. 所选集合里面在同一个地方取走的地雷会不会比该地方题目给出的地雷数多.. 同一个地点可能有多个地雷,如果用去重就不好算多…

题意: 我们定义十进制数x的权值为f(x) = a(n)*2^(n-1)+a(n-1)*2(n-2)+...a(2)*2+a(1)*1,a(i)表示十进制数x中第i位的数字. 题目给出a,b,求出0~b有多少个不大于f(a)的数. 思路: 数位DP,用来学习数位DP了. <数位DP> 所谓数位DP就是基于考虑数字的每一位来转移的DP. 例如求比456小的数,可以这么考虑, 4          5               6   4       5             (0~6) 4…

题目: Determine if a Sudoku is valid, according to: Sudoku Puzzles - The Rules. The Sudoku board could be partially filled, where empty cells are filled with the character '.'. A partially filled sudoku which is valid. Note:A valid Sudoku board (partia…

题目: Given a collection of numbers that might contain duplicates, return all possible unique permutations. For example,[1,1,2] have the following unique permutations:[1,1,2], [1,2,1], and [2,1,1]. 代码: class Solution { public: vector<vector<int>>…

题目: Given a collection of integers that might contain duplicates, nums, return all possible subsets. Note: Elements in a subset must be in non-descending order. The solution set must not contain duplicate subsets. For example,If nums = [1,2,2], a sol…

题目: Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue. Here, we will use the integers 0, 1, and 2 to represent the color red, white, an…

题目: Sort a linked list in O(n log n) time using constant space complexity. 代码: /** * Definition for singly-linked list. * struct ListNode { * int val; * ListNode *next; * ListNode(int x) : val(x), next(NULL) {} * }; */ class Solution { public: ListNo…

题目: Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum. For example:Given the below binary tree and sum = 22, 5 / \ 4 8 / / \ 11 13 4 / \ \ 7 2 1 return…

题目: 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 3 But the following is not: 1 / \ 2 2 \ \ 3 3 Note:Bonus points if you could solve…

题目: Given two binary trees, write a function to check if they are equal or not. Two binary trees are considered equal if they are structurally identical and the nodes have the same value. 代码: /** * Definition for a binary tree node. * struct TreeNode…

题目: Implement wildcard pattern matching with support for '?' and '*'. '?' Matches any single character. '*' Matches any sequence of characters (including the empty sequence). The matching should cover the entire input string (not partial). The functi…

题目: Given two binary strings, return their sum (also a binary string). For example,a = "11"b = "1"Return "100". 代码: class Solution { public: string addBinary(string a, string b) { std::string result; std::string::reverse_iter…

题目: Implement strStr(). Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack. Update (2014-11-02):The signature of the function had been updated to return the index instead of the pointer. If you st…

题目: Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. For example,"A man, a plan, a canal: Panama" is a palindrome."race a car" is not a palindrome. Note:Have you consider tha…

题目: Design and implement a data structure for Least Recently Used (LRU) cache. It should support the following operations: get and set. get(key) - Get the value (will always be positive) of the key if the key exists in the cache, otherwise return -1.…

题目: Given a singly linked list L: L0→L1→…→Ln-1→Ln,reorder it to: L0→Ln→L1→Ln-1→L2→Ln-2→… You must do this in-place without altering the nodes' values. For example,Given {1,2,3,4}, reorder it to {1,4,2,3}. 代码: /** * Definition for singly-linked list.…

题目: Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid. The brackets must close in the correct order, "()" and "()[]{}" are all valid but "(]" and "([)]&…

题目: Given an absolute path for a file (Unix-style), simplify it. For example,path = "/home/", => "/home"path = "/a/./b/../../c/", => "/c" click to show corner cases. Corner Cases: Did you consider the case whe…

题目: Validate if a given string is numeric. Some examples:"0" => true" 0.1 " => true"abc" => false"1 a" => false"2e10" => true Note: It is intended for the problem statement to be ambiguous.…

题意: 给出n个工厂的产品参数带宽b和价格p,在这n个工厂里分别选1件产品共n件,使B/P最小,其中B表示n件产品中最小的b值,P表示n件产品p值的和. 输入 iCase n 表示iCase个样例n个工厂 m1 p1 b1 p2 b2..pm1 bm1 //第一个工厂有m1个同种类不同参数的产品,每一个产品的参数分别是p1 b1 p2 b2 m2 p1 b1 p2 b2..pm2 bm2 ... mn p1 b1 p2 b2..pmn bmn 思路: 排序,先把b从小到大排序,然后把p从小到大排…

题意: 给出一个数组,问你对于第i个数,从最后一个比它大的数到它之间比它小的数中最大的那个数的下标,以及它右边到第一个比它大的数中比它小的数中最大的那一个数的下标<下标从1开始>. eg:5 2 4 3 1  l    0 0 2 0 0        对5来说左边比它小的数没有,所以是0.对2来说左边比它小的数没有,所以是0.对4来说左边比它小的数是2,所以下标是2.  r   3 0 4 5 0         对5来说右边比它小的数中最大的是4,是第3个,所以答案是3.对2来说右边比它小…

题意: 一个炮兵可以攻打和他之间曼哈顿距离为2的士兵,给出你一块n*m的战场,告诉你哪些地方可以站人哪些地方不可以,问你最多可以安放多少个士兵? n <= 100, m <= 10 思路: 这道题暴力是不可以的,因为状态太多了 可以状态DP来做,用一个数组G记录战场的限制,然后用一个数组dp[当前状态或者是前一个状态][当前状态的十进制表示][前一个状态的十进制表示] 因为用的是G[1<<m]来表示,所以时间复杂度是n*(2^m)*(2^m)*(2^m),m最多为10,所以时间复杂…

题目: Given an array of words and a length L, format the text such that each line has exactly L characters and is fully (left and right) justified. You should pack your words in a greedy approach; that is, pack as many words as you can in each line. Pa…

题目: Divide two integers without using multiplication, division and mod operator. If it is overflow, return MAX_INT. 代码: class Solution { public: int divide(int dividend, int divisor) { ) ? INT_MAX : INT_MIN; && dividend==INT_MIN) return INT_MAX; /…

题目: The string "PAYPALISHIRING" is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility) P A H N A P L S I I G Y I R And then read line by line: "PAHNAP…

题目: Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in spiral order. For example,Given the following matrix: [ [ 1, 2, 3 ], [ 4, 5, 6 ], [ 7, 8, 9 ] ] You should return [1,2,3,6,9,8,7,4,5]. 代码: class Solution {…

题目: Given two numbers represented as strings, return multiplication of the numbers as a string. Note: The numbers can be arbitrarily large and are non-negative. 代码: class Solution { public: string multiply(string num1, string num2) { const int n1 = n…

题目: Given a string S and a string T, find the minimum window in S which will contain all the characters in T in complexity O(n). For example,S = "ADOBECODEBANC"T = "ABC" Minimum window is "BANC". Note:If there is no such wind…

题目: Given a collection of intervals, merge all overlapping intervals. For example,Given [1,3],[2,6],[8,10],[15,18],return [1,6],[8,10],[15,18]. 代码: /** * Definition for an interval. * struct Interval { * int start; * int end; * Interval() : start(0),…