C - The Fair Nut and String

CodeForces - 1084C

给出一个序列，求符合规则的序列有多少个，规则有两种，一种是只含a，一种是两个a之间夹着b。

对于每一个a有两种选择，一种是取，一种是不取，例如“aaa”，对应4种选择，a，aa，aaa，0/。为什么会有不取的选择，因为如果取这些a，那么下一波遇到一个a，就可以和这些形成规则2，如果不取，那么下一波遇到的a就代表着规则1。所以每次计数器清零后都应该归1，而不是归0；

#include <iostream>
#include <cstdio>
#include <vector>
#include <stack>
#include <queue>
#include <algorithm>
#include <map>
#include <set>
#include <cmath>
#include <cstring>
#include <string>
#define ll long long
const int mod = 1e9 + 7;
using namespace std;int main()
{string str;ll ans = 0;cin >> str;int len = str.length();ans = 1;ll num = 1;for (int i = 0; i < len; i++) {if (str[i] == 'a') num++;else if (str[i] == 'b') {ans = ans * num % mod;num = 1;}}ans = ans * num % mod;ans -= 1;cout << ans << endl;}

C - The Fair Nut and String相关推荐

【CodeForces - 1084C】The Fair Nut and String（思维，组合数学）
题干: The Fair Nut found a string ss. The string consists of lowercase Latin letters. The Nut is a cur ...
【CodeForces - 1084D】The Fair Nut and the Best Path （树形dp）
题干: The Fair Nut is going to travel to the Tree Country, in which there are nn cities. Most of the l ...
CodeForces 1084A The Fair Nut and Elevator 题解
A. The Fair Nut and Elevator time limit per test : 1 second memory limit per test : 256 megabytes in ...
Codeforces 1084A - The Fair Nut and Elevator
Codeforces 1084A - The Fair Nut and Elevator 题解链接 https://lucien.ink 题目链接 https://codeforces.com/con ...
CodeForces - 1084A The Fair Nut and Elevator 数学
题目 The Fair Nut lives in n story house. ai people live on the i-th floor of the house. Every person ...
CF 1083 A. The Fair Nut and the Best Path
A. The Fair Nut and the Best Path https://codeforces.com/contest/1083/problem/A 题意: 在一棵树内找一条路径,使得从起点 ...
CF1083A The Fair Nut and the Best Path
CF1083A The Fair Nut and the Best Path 先把边权搞成点权(其实也可以不用),那么就是询问树上路径的最大权值. 任意时刻权值非负的限制可以不用管,因为若走路径 \( ...
CodeForces 1084D The Fair Nut and the Best Path（树形dp）
题目描述 The Fair Nut is going to travel to the Tree Country, in which there are n cities. Most of the l ...
codeforces-1084AThe Fair Nut and Elevator-题解
题目大意: Nut在n层的房子里,ai人住在房子的第i-th层,每个人每天使用电梯两次:从他/她住的楼层到一楼,晚上回家时从一楼到他/她住的楼层. 不使用的电梯将停留在X层,(但是X还没有被选择).当 ...

C - The Fair Nut and String

C - The Fair Nut and String

C - The Fair Nut and String相关推荐

最新文章

热门文章