CF3D.Least Cost Bracket Sequence
省选/NOI-
通过率:0%
时间限制:1.00s
内存限制:64MB
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题目描述
This is yet another problem on regular bracket sequences.
A bracket sequence is called regular, if by inserting "+" and "1" into it we get a correct mathematical expression. For example, sequences "(())()", "()" and "(()(()))" are regular, while ")(", "(()" and "(()))(" are not. You have a pattern of a bracket sequence that consists of characters "(", ")" and "?". You have to replace each character "?" with a bracket so, that you get a regular bracket sequence.
For each character "?" the cost of its replacement with "(" and ")" is given. Among all the possible variants your should choose the cheapest.
这又是一道关于正则括号序列的问题。
若能在括号序列中插入 “+” 和 “1” 后得到一个合法的数学表达式,则称该括号序列为正则括号序列。例如,序列 "(())()"、"()" 和 "(()(()))" 是正则括号序列,而 ")("、"(()" 和 "(()))(" 则不是。
你有一个由字符 "("、")" 和 "?" 组成的括号序列模板。你需要将每个字符 "?" 替换为一个括号(即 "(" 或 ")"),使得最终得到一个正则括号序列。
对于每个字符 "?",分别给出了将其替换为 "(" 和 ")" 的代价。在所有可行的替换方案中,你需要选择总代价最小的一种。
输入格式
The first line contains a non-empty pattern of even length, consisting of characters "(", ")" and "?". Its length doesn't exceed 5·104. Then there follow m lines, where m is the number of characters "?" in the pattern. Each line contains two integer numbers a__i and b__i (1 ≤ a__i, b__i ≤ 106), where a__i is the cost of replacing the i-th character "?" with an opening bracket, and b__i — with a closing one.
第一行包含一个非空的、长度为偶数的模式串,由字符 "(", ")" 和 "?" 组成。该模式串的长度不超过 5⋅104。随后是 m 行,其中 m 是模式串中字符 "?" 的个数。每行包含两个整数 ai 和 bi(1≤ai,bi≤106),其中 ai 表示将第 i 个 "?" 替换为左括号 "(" 的代价,bi 表示将其替换为右括号 ")" 的代价。
输出格式
Print the cost of the optimal regular bracket sequence in the first line, and the required sequence in the second.
Print -1, if there is no answer. If the answer is not unique, print any of them.
第一行输出最优规则括号序列的代价,第二行输出对应的序列。
若不存在解,则输出 -1。若解不唯一,输出任意一个即可。
输入输出样例
输入#1
(??) 1 2 2 8
输出#1
4 ()()
输入解题思路,AI测评打分。不知道怎么写?