Educational Codeforces Round 45 (Rated for Div. 2)

A bracket sequence is a string containing only characters "(" and ")".

A regular bracket sequence is a bracket sequence that can be transformed into a correct arithmetic expression by inserting characters "1" and "+" between the original characters of the sequence. For example, bracket sequences "()()", "(())" are regular (the resulting expressions are: "(1)+(1)", "((1+1)+1)"), and ")(" and "(" are not.

You are given nn bracket sequences s1,s2,,sns1,s2,…,sn . Calculate the number of pairs i,j(1i,jn)i,j(1≤i,j≤n) such that the bracket sequence si+sjsi+sj is a regular bracket sequence. Operation ++ means concatenation i.e. "()(" + ")()" = "()()()".

If si+sjsi+sj and sj+sisj+si are regular bracket sequences and iji≠j , then both pairs (i,j)(i,j) and (j,i)(j,i) must be counted in the answer. Also, if si+sisi+si is a regular bracket sequence, the pair (i,i)(i,i) must be counted in the answer.

Input

The first line contains one integer n(1n3105)n(1≤n≤3⋅105) — the number of bracket sequences. The following nn lines contain bracket sequences — non-empty strings consisting only of characters "(" and ")". The sum of lengths of all bracket sequences does not exceed 31053⋅105 .

Output

In the single line print a single integer — the number of pairs i,j(1i,jn)i,j(1≤i,j≤n) such that the bracket sequence si+sjsi+sj is a regular bracket sequence.

Examples
Input
3
)
()
(
Output
 
2
Input
 
2
()
()
Output
4
Note

In the first example, suitable pairs are (3,1)(3,1) and (2,2)(2,2) .

In the second example, any pair is suitable, namely (1,1),(1,2),(2,1),(2,2)(1,1),(1,2),(2,1),(2,2) .

题意:有n个字符串,每个字符串都只有'('和')'组成,从中找出两个字符串可以构成完全匹配的个数(这两个字符串也可以由自己本身组成,如(2,2),(1,1).

题解:所有的字符串可以分为3类:1.自身完美匹配型(即左括号和右括号完美匹配)2:除去完全匹配的子串,剩下的都是左括号,3:除去完全匹配的子串,剩下的都是右括号。对于第一类他的个数ans=c(n,2)*A(2,2)+n(它自身构成的完美匹配),对于第二类和第3类,用map查询一遍(如果有左括号的个数等于右括号的个数,ans=(左括号的种类*右括号的种类),最后不要忘记除去2,因为我们算了两遍。还有一点要注意的是一定要用long long ,我错了好几次才发现这一点。

 1 #include<stdio.h>
 2 #include<string.h>
 3 #include<stack>
 4 #include<string.h>
 5 #include<queue>
 6 #include<algorithm>
 7 #include<iostream>
 8 #include<map>
 9 #include<vector>
10 #define PI acos(-1.0)
11 using namespace std;
12 typedef long long ll;
13 const int MAXN=3e5+10;
14 ll  m;
15 ll ans;
16 char str[MAXN];
17 map<ll ,ll>::iterator it;
18 int main()
19 {
20     ll T;
21     scanf("%lld",&T);
22     map<ll,ll>mp;
23     mp.size();
24     while(T--)
25     {
26         stack<char>s;
27         scanf(" %s",&str);
28         ll len=strlen(str);
29         for(ll i=0;i<len;i++)
30         {
31             if(!s.empty())
32             {
33                 if(s.top()=='('&&str[i]==')')
34                 {
35                     s.pop();
36                 }
37                 else
38                     s.push(str[i]);
39             }
40             else
41             {
42                 s.push(str[i]);
43             }
44         }
45         if(s.empty())
46         {
47             m++;
48         }
49         else
50         {
51             ll cpp=s.size(),flag=0;
52             while(!s.empty())
53             {
54                 if(s.top()=='(')
55                     flag++;
56                 s.pop();
57             }
58             if(flag==0)//栈里面都是右括号
59                 mp[-cpp]++;
60             else if(flag==cpp)//栈里面都是左括号
61             {
62                 mp[cpp]++;
63             }
64         }
65     }
66     for(it=mp.begin();it!=mp.end();it++)
67     {
68         ll k=it->first;
69         if(mp.count(-k))  {
71             ans+=(ll)(it->second*mp[-k]);//左括号的种类*右括号的种类
72         }
73     }
74     printf("%lld
",ans/2+m*m);
75 }
原文地址:https://www.cnblogs.com/moomcake/p/9425384.html