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CodeForces 547E:Mike and Friends(AC自動機+DFS序+主席樹)

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What-The-Fatherland is a strange country! All phone numbers there are strings consisting of lowercase English letters. What is double strange that a phone number can be associated with several bears!

In that country there is a rock band called CF consisting of n bears (including Mike) numbered from 1 to n

.

技術分享圖片

Phone number of i-th member of CF is si. May 17th is a holiday named Phone Calls day. In the last Phone Calls day, everyone called all the numbers that are substrings of his/her number (one may call some number several times). In particular, everyone called himself (that was really strange country).

Denote as call(i, j) the number of times that i-th member of CF called the j-th member of CF.

The geek Mike has q questions that he wants to ask you. In each question he gives you numbers l, r and k and you should tell him the number

技術分享圖片

Input

The first line of input contains integers n

and q (1 ≤ n ≤ 2 × 105 and 1 ≤ q ≤ 5 × 105).

The next n lines contain the phone numbers, i-th line contains a string siconsisting of lowercase English letters (技術分享圖片).

The next q lines contain the information about the questions, each of them contains integers l, r and k (1 ≤ l ≤ r ≤ n and 1 ≤ k ≤ n).

Output

Print the answer for each question in a separate line.

Examples

Input
5 5
a
ab
abab
ababab
b
1 5 1
3 5 1
1 5 2
1 5 3
1 4 5
Output
7
5
6
3
6

題意:給定N個串,M次詢問,每次詢問[L,R]裏含多少個X。

思路:(第一次做,結合主席樹那裏還是不太好想)。對N個串建立AC自動機,建立Fail樹,然後得到DFS序。那麽,對於每個串S,假設其長度為L,S在AC自動機上面跑,其每個前綴Si在AC自動機上面得到最大深度,對應的Fail樹位置,貢獻加1,保證這個貢獻在Si的後綴的子樹裏(比如abcdef,那麽跑到abcd時,在fail樹上面對應的位置貢獻加1 ,對於後綴abcd,bcd,cd,d的子樹都含這個貢獻)。

關鍵是如何出現子樹來自於[L,R]的貢獻。開始我以為以dfs序為X軸,以來自的串為Y軸建立主席樹,查詢的時候查詢區間[in[u],out[u]],即子樹裏關鍵字在[L,R]裏的個數。但是發現沒有轉移關系。所以想不走了。

看了其他人的代碼,是以每個串,以來自的串為X軸(從長的前綴到短的前綴),以dfs序為X軸,保證了前綴和的正確性,查詢的時候查詢區間[L-1,R]的區間在[in[[u],out[u]]的數量。

CodeForces 547E:Mike and Friends(AC自動機+DFS序+主席樹)