2015北京网络赛B题 Mission Impossible 6

借用大牛的一张图片：模拟

 #include<cstdio>
 #include<cmath>
 #include<cstring>
 #include<algorithm>
 #include<iostream>
 #include<memory.h>
 #include<cstdlib>
 #include<vector>
 using namespace std;
 const int MAXN=;
 const double eps=1e-;
 const int inf=0x3f3f3f3f; string s,ss,cs;
 vector<int>pos;
 int mode;
 int now,m;
 void L()
 {
     if(now>)
         now--;
 } void R()
 {
     if(now<ss.length())
         now++;
 } void S()
 {
     mode=!mode;
     pos.clear();
 }
 void C()
 {
     pos.push_back(now);
     if(pos.size()==)
     {
         sort(pos.begin(),pos.end());
         cs=ss.substr(pos[],pos[]-pos[]);
         pos.clear();
     }
 }
 void D()
 {
     if(pos.size())
     {
         pos.push_back(now);
         sort(pos.begin(),pos.end());
         ss.erase(ss.begin()+pos[],ss.begin()+pos[]);
         now=pos[];
         pos.clear();
     }
     else if(now<ss.length())
     {
         ss.erase(ss.begin()+now,ss.begin()+now+);
     }
 } void B()
 {
     if(now>)
     {
         ss.erase(ss.begin()+now-,ss.begin()+now);
         now--;
     }
     pos.clear();
 } void V()
 {
     if(cs.length())
     {
         if(!mode)
         {
             if(ss.length()+cs.length()<=m)
             {
                 int len=cs.length();
                 for(int i=; i<len; i++,now++)
                 {
                     ss.insert(ss.begin()+now,cs[i]);
                 }
             }
         }
         else
         {
             if(now+cs.length()+<=m)
             {
                 int len1=cs.length();
                 int len2=ss.length();
                 for(int i=; i<len1; i++,now++)
                 {
                     if(now>=len2)
                         ss.insert(ss.begin()+now,cs[i]);
                     else
                         ss[now]=cs[i];
                 }
             }
         }
     }
     pos.clear();
 } int main()
 {
     int T;
     scanf("%d",&T);
     while(T--)
     {
         cin>>m>>s;
         int len=s.length();
         mode=;
         now=;
         ss.clear();
         cs.clear();
         pos.clear();
         for(int i=; i<len&&m; i++)
         {
             if(s[i]=='L')
                 L();
             else if(s[i]=='R')
                 R();
             else if(s[i]=='C')
                 C();
             else if(s[i]=='V')
                 V();
             else if(s[i]=='D')
                 D();
             else if(s[i]=='B')
                 B();
             else if(s[i]=='S')
                 S();
             else
             {
                 if(mode&&now<ss.length())
                 {
                     ss[now++]=s[i];
                 }
                 else if(ss.length()<m)
                 {
                     ss.insert(ss.begin()+now,s[i]);
                     now++;
                 }
                 pos.clear();
             }
         }
         if(ss.size())
         {
             cout<<ss<<endl;
         }
         else
             cout<<"NOTHING"<<endl;
     }
     return ;
 }