伪伪的喵喵。。

lightoj 1375题目大意：求小于nn 的数字中，任意两个不相等的数字的lcmlcm和，即∑i=1,j=1,i≠ji=n,j=nlcm(i,j)\displaystyle\sum_{i=1,j=1,i \neq j}^{i=n,j=n}{lcm(i,j)};思路：lcm(1,2)lcm(1,2)  lcm(1,3)lcm(1, 3) lcm(1,4)lcm(1,4) … lcm(1,n)lcm

题目大意：已知k,pk, p，求∑φ(xi)\displaystyle\sum\varphi(x_i), xi=∏kaix_i = {\displaystyle\prod}^k{a_i}, aia_i为素数表前pp的数,其中k≥pk \ge p;思路：φ(p)=φ(n)∗φ(m)\varphi(p) = \varphi(n) * \varphi(m),  其中 p=m∗np = m * n,  gc

lightoj 1336题目大意：已知 x=p1e1∗p2e2∗…∗pkekx = {p_1}^{e_1} * {p_2}^{e_2} * \ldots * {p_k}^{e_k}; σ(x)=∏i=1kpiei+1−1pi−1\sigma(x) = \displaystyle\prod_{i = 1}^k{{{p_i}^{e_i+ 1} - 1} \over{p_i - 1}};求x∈[1,n]x

题目大意：s=a∗bs = a * b; 已知s,amins, a_{min}(最小的aa)问有多少个这样的组合；a≠ba \neq b(没看见错了好几次)思路：s=∏i=1kpeii;ss = \displaystyle\prod_{i = 1}^k{p_i^{e_i}}; s指数分解;Ns的因子个数N_{s的因子个数},=∑i=1k(1+ei)= \displaystyle\sum_{i = 1

lightoj 1356题目大意：给出nn个数分别为aia_i，φ(bi)≥ai\varphi(b_i) \ge a_i, bib_i, 求∑i=1nbi\displaystyle\sum_{i = 1}^nb_i;#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#include <cstdl

lightoj 1028题目大意：求nn的mm进制数，要求最低位为00;思路：即求n的因子个数n=p1q1∗p2q2…pnqn;n = {p_1}^{q_1} * {p_2}^{q_2} \dots {p_n}^{q_n}; ans=∑i=1n(1+qi);ans = \displaystyle\sum_{i=1}^n(1 + q_i); 素数打表，统计nn每个因子的个数； #includ

链接:lightoj题目大意:求递推式： f(n)=∑i=16f(n−i)f(n) = \displaystyle\sum_{i = 1}^6{f(n - i)}解题思路:矩阵快速幂： ⎛⎝⎜⎜⎜⎜⎜⎜⎜⎜⎜f(0)f(1)f(2)f(3)f(4)f(5)⎞⎠⎟⎟⎟⎟⎟⎟⎟⎟⎟∗⎛⎝⎜⎜⎜⎜⎜⎜⎜⎜000001100001010001001001000101000011⎞⎠⎟⎟⎟⎟⎟⎟⎟⎟n

lightoj 1234题目大意：调和级数求和，即:ans=∑i=1n1ians = \displaystyle \sum_{i = 1}^n{1 \over i}思路：分段打标分别求出1∼100,101∼200,…1e8100−99∼1e81001 \sim 100, 101 \sim 200, \dots \displaystyle{{1e8} \over 100} -99 \sim {{1e8

lightoj 1005题目大意:在n×nn \times n的棋盘里摆放kk个车,要求任意两个不在同一行同一列,问有几种方法;思路:从n×nn \times n个里挑一个,n−1×n−1n - 1 \times n - 1个里挑一个…共挑取kk个,再除去他们的顺序;sum=⎛⎝∏n−k+1ni⎞⎠2ksum = {\displaystyle{\left(\displaystyle\prod_{n-