Codeforces 525B Pasha and String

题意：给你一个字符串str ,从1 开始长度为s，每次给你一个 a[i]  ，然后将  [ a[i] , (s-a[i]+1) ]  翻转，问你经过n次操作以后整个字符串是什么样的。

解题思路：

1）根据负负得正的思路，我们只需要从内到外，看那些区域需要翻转，那些区域不需要就行了。

解题代码：

// File Name: b.cpp
// Author: darkdream
// Created Time: 2015年03月27日 星期五 00时33分41秒

#include<vector>
#include<list>
#include<map>
#include<set>
#include<deque>
#include<stack>
#include<bitset>
#include<algorithm>
#include<functional>
#include<numeric>
#include<utility>
#include<sstream>
#include<iostream>
#include<iomanip>
#include<cstdio>
#include<cmath>
#include<cstdlib>
#include<cstring>
#include<ctime>
#define LL long long
#define maxn 200005
using namespace std;
char str[maxn];
int a[maxn];
int cmp(int a, int b)
{
  return a > b; 
}
int n;
void change(int l , int r)
{
    for(int i = l ;i <= r ;i ++)
    {
        swap(str[i],str[n-i+1]);
    }
}
int main(){
     scanf("%s",&str[1]);
     int m ; 
     n = strlen(&str[1]);
     scanf("%d",&m);
     for(int i = 1;i <= m; i ++)
         scanf("%d",&a[i]);
     sort(a+1,a+1+m,cmp);
     int last = n/2; 
     for(int i = 1; i <= m;i ++)
     {
          if((m - i) % 2 == 0) 
          {
            change(a[i],last);
          }
          last = a[i] - 1; 
     }
     puts(&str[1]);
return 0;
}

2）splay  ，我们知道，splay翻转序列只需要logn  所以splay也可以解 .(想法来源是来自于湖大glqAC，被这天大的脑洞吓到了)

// File Name: cf525b.cpp
// Author: darkdream
// Created Time: 2015年04月03日 星期五 22时48分43秒

#include<vector>
#include<list>
#include<map>
#include<set>
#include<deque>
#include<stack>
#include<bitset>
#include<algorithm>
#include<functional>
#include<numeric>
#include<utility>
#include<sstream>
#include<iostream>
#include<iomanip>
#include<cstdio>
#include<cmath>
#include<cstdlib>
#include<cstring>
#include<ctime>
#define LL long long

using namespace std;
const int maxn = 200005;
struct SplayTree{
    int sz[maxn];
    int ch[maxn][2];
    int pre[maxn];
    int n ; 
    int rev[maxn];
    int root ,top1,top2;
    int ss[maxn],que[maxn];
    
    inline void Rotate(int x,int f){
        int y = pre[x];
        push_down(y);
        push_down(x);
        ch[y][!f] = ch[x][f];
        pre[ch[x][f]] = y ; 
        pre[x] = pre[y];
        if(pre[x]) ch[pre[y]][ch[pre[y]][1] == y] = x; 
        ch[x][f] = y ; 
        pre[y] = x ; 
        push_up(y);
    }
    inline void Splay(int x, int goal){
         push_down(x);
         while(pre[x] != goal){
            if(pre[pre[x]] == goal){
                Rotate(x, ch[pre[x]][0] == x);
            }else{
               int y = pre[x],z = pre[y];
               int f = (ch[z][0] == y);
               if(ch[y][f] == x){
                    Rotate(x,!f) , Rotate(x,f);
               }else{
                    Rotate(y,f) , Rotate(x,f);
               }
            }
         }
         push_up(x);
         if(goal ==  0) root = x; 
    }
    inline void RotateTo(int k ,int goal){
        int x = root;
        push_down(x);
        while(sz[ch[x][0]] != k ){
            if(k < sz[ ch[x][0] ]){
                x = ch[x][0];
            }else{
                k -= (sz[ch[x][0]] + 1);
                x = ch[x][1];
            }
            push_down(x);
        }
        Splay(x,goal);
    }
    inline void erase(int x){
        int father = pre[x];
        int head = 0 , tail = 0 ; 
        for(que[tail ++] = x ; head < tail ;head ++){
            ss[top2++] = que[head];
            if(ch[que[head] ][0]) que[tail ++] = ch[que[head]][0];
            if(ch[que[head] ][1]) que[tail ++] = ch[que[head]][1];
        }
        ch[father][ch[father][1] == x] = 0 ;
        push_up(father);
    }
    inline void NewNode(int &x,char c){
         if(top2) x = ss[--top2];
         else x = ++top1;
         ch[x][0] = ch[x][1] = pre[x] = 0 ; 
         sz[x] = 1; 
         rev[x] = 0; 
         val[x] = c;
    }
    inline void push_down(int x){
        if(rev[x])
        {
           swap(ch[x][0],ch[x][1]);
           rev[ch[x][0]] ^= 1 ;
           rev[ch[x][1]] ^= 1 ;
           rev[x] = 0 ; 
        }
    }
    inline void push_up(int x){
         sz[x] = 1 + sz[ch[x][0]] + sz[ch[x][1]];
    }
    inline void makeTree(int &x,int l ,int r,int f){
        if(l > r) return ; 
        int m = (l + r ) >> 1; 
        NewNode(x,str[m]);
        makeTree(ch[x][0],l,m-1,x);
        makeTree(ch[x][1],m+1,r,x);
        pre[x] = f;
        push_up(x);
    }
    inline void init(){
        ch[0][0] = ch[0][1] = pre[0] = sz[0] = 0 ; 
        mx[0] = 0 ; 
        root = top1 = 0 ; 
        NewNode(root,'');
        NewNode(ch[root][1],'');
        pre[top1] = root;
        sz[root] = 2; 
    //    printf("%d***
",mx[root]);

        scanf("%s",&str[1]);
        n = strlen(&str[1]);
        makeTree(ch[ch[root][1]][0],1,n,ch[root][1]);
        push_up(ch[root][1]);
        push_up(root); 

    }
    void print(int x)
    {
       if(x == 0 )
           return; 
       push_down(x);
       print(ch[x][0]);
       printf("%c",val[x]);
       print(ch[x][1]);
    }
    inline void update(int l ,int r){
       RotateTo(l-1,0);
       RotateTo(r+1,root);
       rev[ch[ch[root][1]][0]] ^= 1;
       //Splay(ch[ch[root][1]][0],0);
    }
    inline void query(){
       RotateTo(0,0);
       RotateTo(n+1,root);
       //print(ch[ch[root][1]][0]);
       print(ch[ch[root][1]][0]);
    } 
    char str[maxn];
    char val[maxn];
    int mx[maxn];
}spt;
int ta,tb;
int n , q; 
int main(){
        spt.init();
        //spt.query();
        scanf("%d",&q);
        for(int i = 1;i <= q; i++)
        {
            scanf("%d",&ta);
            spt.update(ta,spt.n-ta+1) ;
        }
        spt.query();
return 0;
}