SGU 397 链表 或者 两个栈。

一开始觉得这个题要平衡树来做。。。

毕竟要动态的插入。。

毕竟啊，平衡树的插入是 logn 的是因为他一开始不知道把元素插入到哪里。

通过寻找，然后才插入的，这个我一开始就知道他应该插入哪里，所以，根本用不着平衡树，链表就OK了。

虽然很简单。。但是是第一次用 STL 的链表

栈 

#include <stdio.h>#include <iostream>#include <queue>#include <algorithm>#include <map>#include <vector>#include <cmath>#include <string.h>#include <stdlib.h>#include <time.h>#include <fstream>#include <set>#include <stack>#include <list>using namespace std;#define READ freopen("acm.in","r",stdin)#define WRITE freopen("acm.out","w",stdout)#define ll long long#define ull unsigned long long #define uint unsigned int#define PII pair<int,int>#define PDD pair<double,double>#define fst first#define sec second#define MS(x,d) memset(x,d,sizeof(x))#define INF 0x3f3f3f3f#define ALL(x) x.begin(),x.end()#define PB push_back#define MOD 99991#define MAX 1111111

链表 

list<char> l;list<char>::iterator it;stack<char> f,b;string s;int main(){    READ;    while(cin>>s)    {        while(!f.empty())            f.pop();        while(!b.empty())            b.pop();        for(int i=0;i<s.size();i++)        {            if(s[i]=='L')                if(!f.empty())                {                    b.push(f.top());                    f.pop();                }            if(s[i]=='R')                if(!b.empty())                {                    f.push(b.top());                    b.pop();                }            if(s[i]>='a'&&s[i]<='z')                f.push(s[i]);        }        while(!f.empty())        {            b.push(f.top());            f.pop();        }        while(!b.empty())        {            printf("%c",b.top());            b.pop();        }        cout<<endl;    }    return 0;}

#include <stdio.h>#include <iostream>#include <queue>#include <algorithm>#include <map>#include <vector>#include <cmath>#include <string.h>#include <stdlib.h>#include <time.h>#include <fstream>#include <set>#include <stack>#include <list>using namespace std;#define READ freopen("acm.in","r",stdin)#define WRITE freopen("acm.out","w",stdout)#define ll long long#define ull unsigned long long #define uint unsigned int#define PII pair<int,int>#define PDD pair<double,double>#define fst first#define sec second#define MS(x,d) memset(x,d,sizeof(x))#define INF 0x3f3f3f3f#define ALL(x) x.begin(),x.end()#define PB push_back#define MOD 99991#define MAX 1111111list<char> l;list<char>::iterator it;stack<char> f,b;string s;int main(){    READ;    while(cin>>s)    {        l.clear();        //cout<<s<<endl;        it=l.begin();        for(int i=0;i<s.length();i++)        {            //cout<<i<<" ";            if(s[i]=='L')                if(it!=l.begin())                    it--;            if(s[i]=='R')                if(it!=l.end())                    it++;            if(s[i]>='a'&&s[i]<='z')                l.insert(it,s[i]);        }        for(it=l.begin();it!=l.end();it++)            cout<<(*it);        cout<<endl;    }    return 0;}