https://codeforc.es/contest/1195/problem/D1 给\(n\)个等长的十进制数串,定义操作\(f(x,y)\)的结果是"从\(y\)的末尾开始一个一个交替放得到的数",求\(\sum\limits_{i=1}^{n}\sum\limits_{j=1}^{n}f(a_i,a_j)\) 很明显每个第\(k\)位(从1开始)都会恰好在\(2k\)和\(2k-1\)位各贡献\(n\)次.预处理出\(pow10\)然后暴力就可以了. #include<…

一.题目 D1. Submarine in the Rybinsk Sea (easy edition) 二.分析 简单版本的话,因为给定的a的长度都是定的,那么我们就无需去考虑其他的,只用计算ai的值在每个位置的贡献即可. 因为长度是定的,如果ai在前,那么对所有的a的贡献就是在偶数位的贡献值然后乘以n即可. 如果ai在后,那么对所有ai的贡献就是在奇数位的贡献值然后乘以n. 将两种情况合并,其实就是求ai在每个位置下的贡献,然后乘以n. 时间复杂度是$O(n)$ 三.AC代码 1 #incl…

https://codeforc.es/problemset/problem/1195/D2 很明显可以看出,任意一个长度为\(l_1\)的数串\(s_1\)和任意一个长度为\(l_2\)的数串\(s_2\)在\(f(s_1,s_2)\)中每个位的贡献的位数是一样的.稍微推一推可以知道,\(calcx\_ijk\)和\(calcy\_ijk\)的公式.然后暴力统计一波各个长度的数串有几个就可以了.小心溢出. #include<bits/stdc++.h> using namespace std…

一.题目 D2. Submarine in the Rybinsk Sea (hard edition) 二.分析 相比于简单版本,它的复杂地方在于对于不同长度,可能对每个点的贡献可能是有差异的. 但是,题目已经说明$a_{i}$最大知道10的9次方,那么$a_{i}$的长度最大也只有10,所以,我们可以按长度进行分组讨论. 需要注意的是,$a_{i}$确定了在前和在后并且确定了$f(a_{i},b_{i})$中的$b_{i}$的长度后,$a_{i}$对各个位置的贡献其实就确定了,相当于对于每一…

除非特别忙,我接下来会尽可能翻译我做的每道CF题的题面! Codeforces 148D 一袋老鼠 Bag of mice | 概率DP 水题 题面 胡小兔和司公子都认为对方是垃圾. 为了决出谁才是垃圾,大哥拿来了一袋老鼠,其中有w只白老鼠和b只黑老鼠.胡小兔先抓,先抓到白老鼠的人赢. 每次学姐抓完老鼠之后,总会有另外一只老鼠从袋子里自己跑出来(这只老鼠不算任何人抓的),而胡小兔抓老鼠时则不会发生这样的事. 每次袋子里的每只老鼠被抓到的概率相等,当有一只老鼠跑出来的时候,每只老鼠跑出来的几率也相…

题目链接:http://codeforces.com/problemset/problem/328/B 水题~ #include <cstdio> #include <cstdlib> #include <cstring> ], a[]; ], c[]; int main(void) { //freopen("in.txt", "r", stdin); scanf("%s%s", n, a); int len1…

A. Fox And Snake 题目连接: http://codeforces.com/contest/510/problem/A Description Fox Ciel starts to learn programming. The first task is drawing a fox! However, that turns out to be too hard for a beginner, so she decides to draw a snake instead. A sna…

A. Vasya the Hipster Time Limit: 1 Sec Memory Limit: 256 MB 题目连接 http://codeforces.com/contest/581/problem/A Description One day Vasya the Hipster decided to count how many socks he had. It turned out that he had a red socks and b blue socks. Accordi…

B. Anatoly and Cockroaches 题目连接: http://codeforces.com/contest/719/problem/B Description Anatoly lives in the university dorm as many other students do. As you know, cockroaches are also living there together with students. Cockroaches might be of tw…

A. Brain's Photos 题目连接: http://www.codeforces.com/contest/707/problem/A Description Small, but very brave, mouse Brain was not accepted to summer school of young villains. He was upset and decided to postpone his plans of taking over the world, but t…