vj- Bear and Strings
Bear and Strings
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
Examples Input bearbtear Output 6
Intput 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).
#include<stdio.h>
#include<string.h>
int main()
{
char s[5010];
while(scanf("%s",s)!=EOF)
{
int len=strlen(s);
int count=0,repeat=0;
for(int i=0;i<len;i++)
{
if(s[i]=='b'&&s[i+1]=='e'&&s[i+2]=='a'&&s[i+3]=='r')
{
count=count+(i+1)*(len-i-3)-repeat*(len-i-3);
repeat=i+1;
}
}
printf("%d\n",count);
}
}
如第二個例子,第一個bear,可以有1*8種,第二個bear出現時,這種演算法,會將第一個bear算進去,所以要減去前一個bear的b出現時的可能。 (世の中には価値がない)