codevs 1743 反转卡片

 1 #include<iostream>
 2 #include<cstdio>
 3 using namespace std;
 4 const int N=300010;
 5 int size[N],c[N][2],rev[N],fa[N],id[N],a[N];
 6 int n,rt;
 7 void pushup(int k){
 8     int l=c[k][0],r=c[k][1];
 9     size[k]=size[l]+size[r]+1;
10 }
11 
12 void pushdown(int k){
13     if (rev[k]){
14         int l=c[k][0],r=c[k][1]; 
15         swap(c[k][1],c[k][0]);
16         rev[l]^=1;rev[r]^=1;
17         rev[k]=0;//第一次k打成l，wa
18     }
19 }
20 
21 void rotate(int x,int &k){
22     int y=fa[x],z=fa[y],l,r;
23     if (c[y][0]==x)l=0;else l=1;r=l^1;
24     if (y==k)k=x;
25     else if (c[z][0]==y)c[z][0]=x; else c[z][1]=x;
26     fa[c[x][r]]=y; fa[x]=z; fa[y]=x;
27     c[y][l]=c[x][r];c[x][r]=y;
28     pushup(y);pushup(x);
29 }
30 
31 void splay(int x,int &k){
32     while (x!=k){//忘记打这一句 wa*2
33         int y=fa[x],z=fa[y];
34         if (y!=k){
35             if (c[z][0]==y^c[y][0]==x) rotate(x,k);
36             else rotate(y,k);
37         }
38         rotate(x,k);
39     }
40 }
41 
42 void build(int l,int r,int f)
43 {
44     if(l>r)return;
45     int mid=(l+r)>>1;
46     if(mid<f)c[f][0]=mid;//这句写错了 wa*3
47     else c[f][1]=mid;
48     size[mid]=1;fa[mid]=f;
49     if(l==r)return;
50     build(l,mid-1,mid);build(mid+1,r,mid);
51     pushup(mid);
52 }
53 
54 int find(int x,int rk){
55     pushdown(x);
56     int l=c[x][0],r=c[x][1];
57     if (size[l]+1==rk) return x;
58     if (size[l]>=rk) return find(l,rk);
59     return find(r,rk-size[l]-1);
60 }
61 
62 void rever(int l,int r){
63     int x=find(rt,l),y=find(rt,r+2);
64     splay(x,rt); splay(y,c[x][1]);
65     int z=c[y][0];//这句写错了wa*4
66     rev[z]^=1;
67 }
68 
69 int main(){
70     scanf("%d",&n);
71     for (int i=2;i<=n+1;i++) scanf("%d",&a[i]);
72     for (int i=1;i<=n+2;i++) id[i]=i;
73     build(1,n+2,0); rt=(n+3)>>1;
74     int sum=0;
75     bool flag=0;
76     while (sum<=100000){
77         int mid=a[find(rt,2)];
78         if (mid==1){
79             flag=1;
80             break;
81         }
82         sum++;
83         rever(1,mid);
84     }
85     if (flag) printf("%d",sum);
86     else printf("-1");
87 }