推荐个做knockout小鼠的公司# Biology - 生物学
p*2
1 楼
前两天有人问DP和Greedy的区别，今天做了一道题不错。我先用DP解，当时感觉有点别
扭，因为觉得好像有条件没有用上，结果超时。后来才意识到这题是Greedy. 想感觉一
下DP和Greedy的可以练练。
Sergey attends lessons of the N-ish language. Each lesson he receives a
hometask. This time the task is to translate some sentence to the N-ish
language. Sentences of the N-ish language can be represented as strings
consisting of lowercase Latin letters without spaces or punctuation marks.
Sergey totally forgot about the task until half an hour before the next
lesson and hastily scribbled something down. But then he recollected that in
the last lesson he learned the grammar of N-ish. The spelling rules state
that N-ish contains some "forbidden" pairs of letters: such letters can
never occur in a sentence next to each other. Also, the order of the letters
doesn't matter (for example, if the pair of letters "ab" is forbidden, then
any occurrences of substrings "ab" and "ba" are also forbidden). Also, each
pair has different letters and each letter occurs in no more than one
forbidden pair.
Now Sergey wants to correct his sentence so that it doesn't contain any "
forbidden" pairs of letters that stand next to each other. However, he is
running out of time, so he decided to simply cross out some letters from the
sentence. What smallest number of letters will he have to cross out? When a
letter is crossed out, it is "removed" so that the letters to its left and
right (if they existed), become neighboring. For example, if we cross out
the first letter from the string "aba", we get the string "ba", and if we
cross out the second letter, we get "aa".
Input
The first line contains a non-empty string s, consisting of lowercase Latin
letters — that's the initial sentence in N-ish, written by Sergey. The
length of string s doesn't exceed 105.
The next line contains integer k (0 ≤ k ≤ 13) —
the number of forbidden pairs of letters.
Next k lines contain descriptions of forbidden pairs of letters. Each line
contains exactly two different lowercase Latin letters without separators
that represent the forbidden pairs. It is guaranteed that each letter is
included in no more than one pair.
Output
Print the single number — the smallest number of letters that need to be
removed to get a string without any forbidden pairs of neighboring letters.
Please note that the answer always exists as it is always possible to remove
all letters.
Sample test(s)
input
ababa
1
ab
output
2
input
codeforces
2
do
cs
output
1
扭，因为觉得好像有条件没有用上，结果超时。后来才意识到这题是Greedy. 想感觉一
下DP和Greedy的可以练练。
Sergey attends lessons of the N-ish language. Each lesson he receives a
hometask. This time the task is to translate some sentence to the N-ish
language. Sentences of the N-ish language can be represented as strings
consisting of lowercase Latin letters without spaces or punctuation marks.
Sergey totally forgot about the task until half an hour before the next
lesson and hastily scribbled something down. But then he recollected that in
the last lesson he learned the grammar of N-ish. The spelling rules state
that N-ish contains some "forbidden" pairs of letters: such letters can
never occur in a sentence next to each other. Also, the order of the letters
doesn't matter (for example, if the pair of letters "ab" is forbidden, then
any occurrences of substrings "ab" and "ba" are also forbidden). Also, each
pair has different letters and each letter occurs in no more than one
forbidden pair.
Now Sergey wants to correct his sentence so that it doesn't contain any "
forbidden" pairs of letters that stand next to each other. However, he is
running out of time, so he decided to simply cross out some letters from the
sentence. What smallest number of letters will he have to cross out? When a
letter is crossed out, it is "removed" so that the letters to its left and
right (if they existed), become neighboring. For example, if we cross out
the first letter from the string "aba", we get the string "ba", and if we
cross out the second letter, we get "aa".
Input
The first line contains a non-empty string s, consisting of lowercase Latin
letters — that's the initial sentence in N-ish, written by Sergey. The
length of string s doesn't exceed 105.
The next line contains integer k (0 ≤ k ≤ 13) —
the number of forbidden pairs of letters.
Next k lines contain descriptions of forbidden pairs of letters. Each line
contains exactly two different lowercase Latin letters without separators
that represent the forbidden pairs. It is guaranteed that each letter is
included in no more than one pair.
Output
Print the single number — the smallest number of letters that need to be
removed to get a string without any forbidden pairs of neighboring letters.
Please note that the answer always exists as it is always possible to remove
all letters.
Sample test(s)
input
ababa
1
ab
output
2
input
codeforces
2
do
cs
output
1
