Longest Regular Bracket Sequence
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This is yet another problem dealing with regular bracket sequences.
We should remind you that a bracket sequence is called regular, if by inserting «+» and «1» into it we can get a correct mathematical expression. For example, sequences «(())()», «()» and «(()(()))» are regular, while «)(», «(()» and «(()))(» are not.
You are given a string of «(» and «)» characters. You are to find its longest substring that is a regular bracket sequence. You are to find the number of such substrings as well.
The first line of the input file contains a non-empty string, consisting of «(» and «)» characters. Its length does not exceed 106.
Print the length of the longest substring that is a regular bracket sequence, and the number of such substrings. If there are no such substrings, write the only line containing "0 1".
)((())))(()())
6 2
))(
0 1
题目大意:给出一个括号字符串,求出它的最大合法字串的长度和最大长度的个数,当最大合法字串长度为0时,输出“0 1”。
思路:利用栈进行维护,每读入一个左括号就将它的下标压栈,每读入一个右括号就将它出栈,因为每一个合法的括号匹配,右括号一定与当前的栈顶左括号匹配,令一个vis[]数组,初始化为0,每次读到右括号就将当前位置和栈顶位置的vis置为1,最后遍历一遍vis数组,找出最大长度连续1的个数以及最大长度的个数即可。注意:最大长度为0时答案需要特判。
参考代码:
#include<iostream>#include<cstdio>#include<cstring>#include<string>#include<algorithm>#include<queue>#include<stack>#include<vector>#include<cmath>#include<set>#include<map>#include<cstdlib>#include<functional>#include<climits>#include<cctype>#include<iomanip>using namespace std;typedef long long ll;#define INF 0x3f3f3f3f#define mod 1e9+7#define clr(a,x) memset(a,x,sizeof(a))const double eps = 1e-6;stack <int> Q;char str[1000010];int vis[1000010];void Clear(){ while(!Q.empty()) Q.pop();}int main(){ while(scanf("%s",str)==1) { int len=strlen(str); int ans=0; //记录最大长度的个数 int maxn=0; //记录最大长度 int cnt=0; //计数器 Clear(); //每次都要将栈清空 clr(vis,0); //将vis初始化为0 for(int i=0;i<len;i++) { if(str[i]=='(') Q.push(i); if(str[i]==')') { if(!Q.empty()) { vis[i]=1; vis[Q.top()]=1; //将栈顶位置和当前位置的vis置为1 Q.pop(); } else continue; } } vis[len]=0; //强行将lenth位置的元素置为0,防止继续遍历下去 for(int i=0;i<=len;i++) { if(vis[i]==1) { cnt++; //如果vis为1,就++ } if(vis[i]==0) { if(maxn<cnt) //读到0时,比较最大长度与读到0之前1的个数,如果小于 { maxn=cnt; //每次都找到最大的长度 ans=1; //说明最大的长度更长,则,最大长度的数量重现置为1 cnt=0; //将cnt清0 } else if(maxn==cnt) //如果相等,就将最大长度数量加一 { ans++; cnt=0; } else //如果大于,只将cnt清零 cnt=0; } } if(maxn) cout<<maxn<<" "<<ans<<endl; else puts("0 1"); //当最后遍历完之后发现maxn就每变过,说明就没有找到一个合法匹配的括号,则输出0 1 } return 0;}
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