嗯... 题目链接:https://www.luogu.org/problemnew/show/CF804B 这道题没有什么技巧,只是一道找规律的题. 首先看到“ab”可以换成“bba”,所以首先要确定我们要逆序枚举(注意s从s_0开始),如果遇到a,则把ans += cntb,因为可以换的次数即为a后面b的个数,然后把cntb的个数乘二,因为一个ab可以换bba,也就一个b换两个b.如果遇到b,则直接cntb++即可,不需要别的操作. 注:mod可以随时模,不会影响最后结果. AC代码: #i…

思路: 找规律.参考了http://blog.csdn.net/harlow_cheng/article/details/71190999. 实现: #include <iostream> using namespace std; ; int main() { string s; cin >> s; int n = s.length(); ; ; ; i < n; i++) { % mod; ) % mod; } cout << sum << endl…

D. Minimum number of steps time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output We have a string of letters 'a' and 'b'. We want to perform some operations on it. On each step we choose one of s…

D. Minimum number of steps time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output We have a string of letters 'a' and 'b'. We want to perform some operations on it. On each step we choose one of s…

cf劲啊 原题: We have a string of letters 'a' and 'b'. We want to perform some operations on it. On each step we choose one of substrings "ab" in the string and replace it with the string "bba". If we have no "ab" as a substring,…

http://codeforces.com/contest/805/problem/D D. Minimum number of steps time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output We have a string of letters 'a' and 'b'. We want to perform some opera…

805D - Minimum number of steps 思路:简单模拟,a每穿过后面一个b,b的个数+1,当这个a穿到最后,相当于把它后面的b的个数翻倍.每个a到达最后的步数相当于这个a与它后面已经到达最后的a之间的b的个数,只要从后面往前扫,记录b的个数,每遇到一个a,把b的个数加入答案,并且b的个数翻倍. 代码: #include<bits/stdc++.h> using namespace std; const int INF=0x3f3f3f3f; ; ; int main()…

D. Minimum number of steps time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output We have a string of letters 'a' and 'b'. We want to perform some operations on it. On each step we choose one of s…

P1348 Couple number 题目描述 任何一个整数N都能表示成另外两个整数a和b的平方差吗?如果能,那么这个数N就叫做Couple number.你的工作就是判断一个数N是不是Couple number. 输入输出格式 输入格式: 仅一行,两个长整型范围内的整数n1和n2,之间用1个空格隔开. 输出格式: 输出在n1到n2范围内有多少个Couple number. 注意:包括n1和n2两个数,且n1<n2,n2 - n1 <= 10 000 000. 输入输出样例 输入样例#1: …

题目描述 任何一个整数N都能表示成另外两个整数a和b的平方差吗?如果能,那么这个数N就叫做Couple number.你的工作就是判断一个数N是不是Couple number. 输入输出格式 输入格式: 仅一行,两个长整型范围内的整数$n_1$和$n_2$,之间用1个空格隔开. 输出格式: 输出在$n_1$到$n_2$范围内有多少个Couple number. 注意:包括$n_1$和$n_2$两个数,且$n_1<n_2,n_2 - n_1 \leqslant 10^7$. 输入输出样例 输入样例…