Power Strings Time Limit: 3000MS   Memory Limit: 65536K Total Submissions: 41252   Accepted: 17152 Description Given two strings a and b we define a*b to be their concatenation. For example, if a = "abc" and b = "def" then a*b = "…

Power Strings 题意 给出一个字符串s,求s最多由几个相同的字符串重复而成(最小循环节的重复次数) 思路 之前学习KMP的时候做过. 我的思路是:枚举字符串的长度,对于当前长度k,判断\(lcp(1,k+1)>=k\),\(lcp(k+1,2k+1)>=k\),\(lcp(3k+1,4k+1)>=k\)....是否都成立 但这样复杂度有点高,就找了一下题解. 其实只需要判断\(lcp(1,k+1)\)是否是\(n-k\)就可以了. 具体原理如下图: 参考博客 对于\(lcp(…

看的<后缀数组——处理字符串的有力工具>这篇论文,在那里这道题是用后缀数组实现的,复杂度为$O(nlogn)$,很明显长度为$2×10^6$的数据会TLE,所以必需得用复杂度为$O(n)$的KMP算法.第一次写KMP,我好弱啊QAQ KMP: #include<cstdio> #include<cstring> #include<algorithm> using namespace std; const int N = 2000003; char s[N];…

终于靠着理解写出KMP了,两种KMP要代码中这种才能求循环节.i-next[i]就是循环节. #include<cstdio> #define N 1000005 char s[N]; int next[N]; void solve(){ int ans; int k=-1,i=0; next[i]=k; while(s[i]){ if(k==-1||s[i]==s[k]){//记住两个都是等于 i++; k++; next[i]=k; }else k=next[k]; } ans=i-nex…

[题目链接] 点击打开链接 [算法] KMP 如果字符串中存在循环节,则next[len] = (循环节个数 - 1) * 循环节长度 循环节个数 = len / (len - next[len]) [代码] #include <algorithm> #include <bitset> #include <cctype> #include <cerrno> #include <clocale> #include <cmath> #in…

http://poj.org/problem?id=1459 题意:有np个发电站,nc个消费者,m条边,边有容量限制,发电站有产能上限,消费者有需求上限问最大流量. 思路:S和发电站相连,边权是产能上限,消费者和T相连,边权是需求上限,边的话就按题意加就好了.难点更觉得在于输入..加个空格..边数组要*2,因为有反向边. #include <cstdio> #include <algorithm> #include <iostream> #include <cs…

Power of Cryptography Time Limit: 1000MS   Memory Limit: 30000K Total Submissions: 18258   Accepted: 9208 Description Current work in cryptography involves (among other things) large prime numbers and computing powers of numbers among these primes. W…

描述 Given two strings a and b we define a*b to be their concatenation. For example, if a = "abc" and b = "def" then a*b = "abcdef". If we think of concatenation as multiplication, exponentiation by a non-negative integer is de…

http://poj.org/problem?id=2406 就是给一个串,求其循环节的个数. 稍微想一下就知道,KMP中nxt数组记录了所有可与前面匹配的位置. 那么如果我们的循环节长度为k,有n个,那么我们最后一个nxt显然就会是k*(n-1). 倒推即可. #include<cstdio> #include<cstring> using namespace std; ]; ]={}; void getnext(int m){ ; ;i<=m;i++){ &&am…

Surprising Strings Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 6258   Accepted: 4072 Description The D-pairs of a string of letters are the ordered pairs of letters that are distance D from each other. A string is D-unique if all of…