思路显然是暴力枚举. 但是两个问题: 1.当1的位数非常大时,模运算很费时间,会超时. 其实每次不用完全用'11111...'来%K,上一次的余数*10+1后再%K就行. 证明: 令f(n)=111111...(n个1); g(n)=f(n)%K 因为f(n)=f(n-1)*10+1 所以f(n)%K=(f(n-1)*10+1)%K 即g(n)=g(n-1)*10+1 2.枚举何时停止? 一种方法是可以设置一个大数,比如10的6次方,可以Accepted. 更精确的方法是:从1个1到K个1,如果…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 日期 题目地址:https://leetcode.com/problems/smallest-integer-divisible-by-k/ 题目描述 Given a positive integer K, you need find the smallest positive integer N such that N is divisible b…

题目如下: Given a positive integer K, you need find the smallest positive integer N such that N is divisible by K, and N only contains the digit 1. Return the length of N.  If there is no such N, return -1. Example 1: Input: 1 Output: 1 Explanation: The…

Given a positive integer K, you need find the smallest positive integer N such that N is divisible by K, and N only contains the digit 1. Return the length of N.  If there is no such N, return -1. Example 1: Input: 1 Output: 1 Explanation: The smalle…

A sorted list A contains 1, plus some number of primes.  Then, for every p < q in the list, we consider the fraction p/q. What is the K-th smallest fraction considered?  Return your answer as an array of ints, where answer[0] = pand answer[1] = q. Ex…

前缀和(prefix sum/cumulative sum)的应用. 还用了一个知识点: a≡b(mod d) 则 a-b被d整除. 即:a与b对d同余,则a-b被d整除. class Solution(object): def subarraysDivByK(self, A, K): P = [0] for x in A: P.append((P[-1] + x) % K) count = collections.Counter(P) return sum(v*(v-1)/2 for v in…

Given integers n and k, find the lexicographically k-th smallest integer in the range from 1 to n. Note: 1 ≤ k ≤ n ≤ 109. Example: Input: n: 13 k: 2 Output: 10 Explanation: The lexicographical order is [1, 10, 11, 12, 13, 2, 3, 4, 5, 6, 7, 8, 9], so…

Given a n x n matrix where each of the rows and columns are sorted in ascending order, find the kth smallest element in the matrix. Note that it is the kth smallest element in the sorted order, not the kth distinct element. Example: matrix = [ [ 1, 5…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 目录 题目描述 题目大意 解题方法 动态规划 前缀和求余 日期 题目地址:https://leetcode.com/problems/subarray-sums-divisible-by-k/ 题目描述 Given an array A of integers, return the number of (contiguous, non-empty) subarrays that ha…

Given an array A of integers, return the number of (contiguous, non-empty) subarrays that have a sum divisible by K. Example 1: Input: A = [4,5,0,-2,-3,1], K = 5 Output: 7 Explanation: There are 7 subarrays with a sum divisible by K = 5: [4, 5, 0, -2…