Musical ThemesBrian Dean A musical melody is represented as a sequence of N (1 <= N <= 5000) notes that are integers in the range 1..88, each representing a key on the piano. It is unfortunate but true that this representation of melodies ignores th…

直接枚举O(n^3)会TLE,只要稍微加点优化,在不可能得到更优解时及时退出.其实就是道水题,虽说我提交了6次才过= =..我还太弱了 -------------------------------------------------------------------------- #include<cstdio> #include<iostream> #include<cstring> #include<algorithm> #include<cc…

P2743 乐曲主题Musical Themes(poj1743) 然后呢这题思路其实还是蛮简单的,只是细节特别多比较恶心,忘记了差分带来的若干疏漏.因为转调的话要保证找到相同主题,只要保证一段内相对的差值不变,所以自然而然想到差分.注意细节.1.因为差分会带来负数,而负数在后缀数组里最初排名是会出问题的,所以要全搞成正的,+100即可2.因为最后一位不可以计算入差分数组里,所以不算,n要减1,同时二分答案后要记得把求得的最长差分长度加上一才是原数组长度3.最坑的地方是找不重复的最长字串,自然套…

[题目]F. k-substrings [题意]给定长度为n的串S,对于S的每个k-子串$s_ks_{k+1}...s_{n-k+1},k\in[1,\left \lceil \frac{n}{2} \right \rceil]$,找到满足[奇数长度][严格子串][同时是前缀和后缀]的最长子串.n<=10^6. [算法]字符串哈希+二分 [题解]任意两个对应子串,它们有一个不变量——它们的中心一定是i和n-i+1.而且固定中心之后,能延伸的最长相等子串是可以二分+哈希得到的. 所以枚举k,二分+…

Time Limit: 1000MS   Memory Limit: 30000K Total Submissions: 33462   Accepted: 11124 Description A musical melody is represented as a sequence of N (1<=N<=20000)notes that are integers in the range 1..88, each representing a key on the piano. It is…

Musical Theme Time Limit: 1000MS Memory Limit: 30000K Total Submissions: 28435 Accepted: 9604 Description A musical melody is represented as a sequence of N (1<=N<=20000)notes that are integers in the range 1..88, each representing a key on the pian…

LOJ 被一件不愉快的小事浪费了一个小时= =. 表示自己(OI方面的)智商没救了=-= 比较显然 二分+树哈希.考虑对树的括号序列进行哈希. 那么每个点的\(k\)子树的括号序列,就是一段区间去掉距离它为\(k+1\)的点的子树的区间.那么我们把每个点放到它的\(k+1\)级祖先上,在\(k+1\)级祖先处求哈希值时,跳过这个点的括号区间即可. 至于具体的哈希方式...xjb哈希就行了 //672ms 24.97M #include <cstdio> #include <cctype&…

传送门   题解 听说大佬们这题都是用SA秒掉的 然而SA的时间复杂度的确很优秀,缺点就是看不太懂…… 然后发现一位大佬用哈希华丽的过了此题,而且讲的特别清楚->这里 我们只要考虑以每一个点结尾的$AA$串的个数$u[i]$和以每一个点开头的AA串的个数$v[i]$,答案就是$\sum _{i=1}^{n-1} u[i]*v[i+1]$ 那么考虑如何求出$u$和$v$呢 我们考虑一下,枚举串$A$的长度$len$,然后每隔$len$个单位设置一个关键点.不难发现,每一个长度为$len*2$的$A…

During a discussion of problems at the Petrozavodsk Training Camp, Vova and Sasha argued about who of them could in 300 minutes find a pair of equal squares of the maximal size in a matrix of size N × M containing lowercase English letters. Squares c…

先把两个串能匹配模式串的位置找出来,然后标记为$1$(标记在开头或末尾都行),然后对标记数组求一个前缀和,这样可以快速查到区间内是否有完整的一个模式串. 然后二分子串(答案)的长度,每次把长度为$md$的串扔到哈希表里,查一波匹不匹配. #include<cstdio> #include<iostream> #include<algorithm> #include<cstring> #define ull unsigned long long #define…