序列计数 Time Limit: 4500/4000 MS (Java/Others)    Memory Limit: 262144/262144 K (Java/Others)Total Submission(s): 348    Accepted Submission(s): 117 Problem Description 度度熊了解到,1,2,…,n 的排列一共有 n!=n×(n−1)×⋯×1 个.现在度度熊从所有排列中等概率随机选出一个排列 p1,p2,…,pn,你需要对 k=1,2,…

There is an apple tree outside of kaka's house. Every autumn, a lot of apples will grow in the tree. Kaka likes apple very much, so he has been carefully nurturing the big apple tree. The tree has N forks which are connected by branches. Kaka numbers…

http://acm.hdu.edu.cn/showproblem.php?pid=5542 [题意] 给定长为n的序列,问有多少个长为m的严格上升子序列? [思路] dp[i][j]表示以a[i]结尾的长度为j的严格上升子序列有多少个 dp[i][j]=sum{dp[k][j-1]},k小于i且a[k]<a[i] 区间dp,复杂度为O(n^3) 会超时,第三层循环求和用树状数组加速 时间复杂度为O(n^2logn) 离散化的时候排序后不去重(否则WA) [Accepted] #include<…

题意:给你一个字符串和m个询问,问你l,r这个区间内出现过多少字串. 连接:http://acm.hdu.edu.cn/showproblem.php?pid=4622 网上也有用后缀数组搞得. 思路(虎哥):用字典树把每一个字符串对应成一个整数 相同的字符串对应到相同的整数上 把所用的串对应的整数放在一个数组里 比如书字符串s[l...r]对应的整数是 k 那么二维数组 [l][r] 就等于k 假设一个对应好的二维数组  左下角是原点 3     4     5     2 2     3  …

Wavel Sequence Problem Description Have you ever seen the wave? It's a wonderful view of nature. Little Q is attracted to such wonderful thing, he even likes everything that looks like wave. Formally, he defines a sequence a1,a2,...,an as ''wavel'' i…

Increasing Speed Limits Time Limit: 2000/10000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 481    Accepted Submission(s): 245 Problem Description You were driving along a highway when you got caught by the road p…

Find the nondecreasing subsequences Time Limit: 10000/5000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 1844    Accepted Submission(s): 677 Problem Description How many nondecreasing subsequences can you find in t…

题意: 二维平面上N个点,从(0,0)出发到(1e9,1e9),每次只能往右,上,右上三个方向移动, 该N个点只有从它的左下方格点可达,此时可获得收益.求该过程最大收益. 分析:我们很容易就可以想到用DP,假设这个位置是相对上一个位置的方向而来,但是复杂度达到N^2 ,这样是不行的: 我们可以利用坐标的信息,将所有的点离散化后,以x优先按小到大排序,按y按大到小排序,这时维护一个DP(i) ,表示第I列的最值. j=0→i−1j=0→i−1                           d…

Ordered Subsequence Time Limit: 4000/2000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 464    Accepted Submission(s): 216 Problem Description A numeric sequence of ai is ordered if a1<a2<……<aN. Let the subsequ…

题目链接:http://codeforces.com/contest/597/problem/C 给你n和数(1~n各不同),问你长为k+1的上升自序列有多少. dp[i][j] 表示末尾数字为i 长度为j的上升子序列个数,但是dp数组是在树状数组的update函数中进行更新. update(i, val, j)函数表示在i的位置加上val,更新dp[i][j]. sum(i, j)就是求出末尾数字小于等于i 且长度为j的子序列有多少个. //#pragma comment(linker, "/…