题目链接 题目大意 给你一个长为d只包含字符'a','b','c','?' 的字符串,?可以变成a,b,c字符,假如有x个?字符,那么有\(3^x\)个字符串,求所有字符串种子序列包含多少个abc子序列 题目思路 假如没有问号,那么就是一个简单的dp \(dp[i][1]为前i个位置有多少个a\) \(dp[i][2]为前i个位置有多少个ab\) \(dp[i][3]为前i个位置有多少个abc\) 考虑 '?' 会对 dp 的转移产生什么影响,因为 '?' 可以将三种字母全部都表示一遍,所以到了…

Friends and Subsequences 题解: 如果左端点来说, 那么对于a[i]来说是向上的一条折线, b[i]来说是向下的一条折线, 那么如果这2个折线求交点个数的话, 我们可以二分去求第一个 a[i] == b[i] 的地方, 求最后一个a[i] == b[i]的地方. 代码: #include<bits/stdc++.h> using namespace std; #define Fopen freopen("_in.txt","r",…

DFS基础 深度优先搜索(Depth First Search)是一种搜索思路,相比广度优先搜索(BFS),DFS对每一个分枝路径深入到不能再深入为止,其应用于树/图的遍历.嵌套关系处理.回溯等,可以用递归.堆栈(stack)实现DFS过程. 关于广度优先搜索(BFS)详见:算法与数据结构基础 - 广度优先搜索(BFS) 关于递归(Recursion)详见:算法与数据结构基础 - 递归(Recursion) 树的遍历 DFS常用于二叉树的遍历,关于二叉树详见: 算法与数据结构基础 - 二叉查找树…

题目来源: https://leetcode.com/problems/distinct-subsequences/ 题意分析: 给定字符串S和T,判断S中可以组成多少个T,T是S的子串. 题目思路: 这是一个动态规划的问题.设定ans[i][j]为s[:i] 组成t[:j]的个数.那么动态规划方程为,if s[i - 1] == t[j - 1]: ans[i][j] = ans[i - 1][j - 1] + ans[i - 1][j]:else: ans[i][j] = ans[i - 1…

博客搬至blog.csgrandeur.com,cnblogs不再更新. 新的题解会更新在新博客:http://blog.csgrandeur.com/2014/01/15/LeetCode-OJ-Solution/ ———————————————————————————————————————— ———————————————————————————————————————— LeetCode OJ 题解 LeetCode OJ is a platform for preparing tech…

Friends and Subsequences 题目链接: http://acm.hust.edu.cn/vjudge/contest/121333#problem/H Description Mike and !Mike are old childhood rivals, they are opposite in everything they do, except programming. Today they have a problem they cannot solve on the…

C. Subsequences Time Limit: 20 Sec Memory Limit: 256 MB 题目连接 http://codeforces.com/contest/597/problem/C Description For the given sequence with n different elements find the number of increasing subsequences with k + 1 elements. It is guaranteed tha…

题目: Given a string S and a string T, count the number of distinct subsequences of T in S. A subsequence of a string is a new string which is formed from the original string by deleting some (can be none) of the characters without disturbing the relat…

Problem Description How many nondecreasing subsequences can you find in the sequence S = {s1, s2, s3, ...., sn} ? For example, we assume that S = {1, 2, 3}, and you can find seven nondecreasing subsequences, {1}, {2}, {3}, {1, 2}, {1, 3}, {2, 3}, {1,…

题目链接 题目要求: Given a string S and a string T, count the number of distinct subsequences of T in S. A subsequence of a string is a new string which is formed from the original string by deleting some (can be none) of the characters without disturbing th…