Codeforces Round #226 (Div. 2) B. Bear and Strings

本文主要是介绍Codeforces Round #226 (Div. 2) B. Bear and Strings，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

The bear has a string s = s1s2... s|s| (record |s| is the string's length), consisting of lowercase English letters. The bear wants to count the number of such pairs of indices i, j (1 ≤ i ≤ j ≤ |s|), that string x(i, j) = sisi + 1... sj contains at least one string "bear" as a substring.

String x(i, j) contains string "bear", if there is such index k (i ≤ k ≤ j - 3), that sk = b, sk + 1 = e, sk + 2 = a, sk + 3 = r.

Help the bear cope with the given problem.

Input

The first line contains a non-empty string s (1 ≤ |s| ≤ 5000). It is guaranteed that the string only consists of lowercase English letters.

Output

Print a single number — the answer to the problem.

Sample test(s) 
input 
bearbtear
output 
6
input 
bearaabearc
output 
20

Note

In the first sample, the following pairs (i, j) match: (1, 4), (1, 5), (1, 6), (1, 7), (1, 8), (1, 9).

In the second sample, the following pairs (i, j) match: (1, 4), (1, 5), (1, 6), (1, 7), (1, 8), (1, 9), (1, 10), (1, 11), (2, 10), (2, 11), (3, 10), (3, 11), (4, 10), (4, 11), (5, 10), (5, 11), (6, 10), (6, 11), (7, 10), (7, 11).

做了这么多场第一次被黑

附上截图：

本来还想着这次rating应该会有所进步吧，结果华丽丽被黑了。。。

最关键的是我没在第一时间注意到，当我交第三题的时候才看到

导致我改过来的时候已经快结束了。。。这次肯定又要跌

题目还是比较简单的，找到公式就好。

我的公式是：ans += (i+1-times)*(k-i-3)

i是当前“bear”出现处i对应的下标

k是str.size()，之所以不用str.size()；是因为在循环中，用str.size()每次都要计算

times代表上次出现bear处b的下标，初始化为0;

另外我的下标是从0开始的，请看客们对号入座哈

又改了一下，因为题目还没判出来，不知道改的对不对

刚刚发现我过了，好多人都wa掉了，不知道是不是和我之前犯的一样的错

感谢黑我的兄弟

之前的代码是没有考虑输入字符串长度小于4的情况。

先贴上代码睡觉吧，明天再看

#include <iostream>
#include <string>
#include <vector>
#define rep(i,j,k) for(int i=(j); i<k; i++)
#define long long ll
using namespace std;
int main(void){string str;while(cin >> str){int ans = 0;int times = 0;int k = str.size();if(k>3){for(int i=0; i<k-3; ++i)if(str[i]=='b'&&str[i+1]=='e'&&str[i+2]=='a'&&str[i+3]=='r'){ans += (i+1-times)*(str.size()-i-3);times = i+1;}}cout << ans << endl;}return 0;
}

这篇关于Codeforces Round #226 (Div. 2) B. Bear and Strings的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！