UVA11922--Permutation Transformer (伸展树Splay)

题意：m条操作指令，对于指令 a b 表示取出第a~b个元素，翻转后添加到排列的尾部。
水题卡了一个小时，一直过不了样例。原来是 dfs输出的时候忘记向下传递标记了。
  1 #include <cstdio>
  2 #include <cstdlib>
  3 #include <cstring>
  4 #include <algorithm>
  5 using namespace std;
  6 const double eps = 1e-8;
  7 const int maxn = 100086;
  8 int siz[maxn],pre[maxn],ch[maxn][2],rev[maxn],key[maxn];
  9 int n,m,tot,root;
 10 void update_rev(int r)
 11 {
 12     if (!r)
 13         return;
 14     swap(ch[r][0],ch[r][1]);
 15     rev[r] ^= 1;
 16 }
 17 void push_up(int r)
 18 {
 19     siz[r] = siz[ch[r][0]] + siz[ch[r][1]] + 1;
 20 }
 21 void push_down(int r)
 22 {
 23     if (rev[r])
 24     {
 25         update_rev(ch[r][0]);
 26         update_rev(ch[r][1]);
 27         rev[r] = 0;
 28     }
 29 }
 30 void NewNode(int &r,int father,int k)
 31 {
 32     r = ++tot;
 33     pre[r] = father;
 34     ch[r][0] = ch[r][1] = 0;
 35     key[r] = k;
 36     rev[r] = 0;
 37     siz[r] = 1;
 38 }
 39 void build(int &x,int l,int r,int father)
 40 {
 41     if (l > r)
 42         return;
 43     int mid = (l + r) >> 1;
 44     NewNode(x,father,mid);
 45     build(ch[x][0],l,mid-1,x);
 46     build(ch[x][1],mid+1,r,x);
 47     push_up(x);
 48 }
 49 void init()
 50 {
 51     root = tot = 0;
 52     NewNode(root,0,-1);
 53     NewNode(ch[root][1],root,-1);
 54     build(ch[ch[root][1]][0],1,n,ch[root][1]);
 55     push_up(root);
 56     push_up(ch[root][1]);
 57 }
 58 void Rotate(int x,int kind)
 59 {
 60     int y = pre[x];
 61     push_down(y);
 62     push_down(x);
 63     ch[y][!kind] = ch[x][kind];
 64     pre[ch[x][kind]] = y;
 65     if (pre[y])
 66         ch[pre[y]][ch[pre[y]][1] == y] = x;
 67     pre[x] = pre[y];
 68     ch[x][kind] = y;
 69     pre[y] = x;
 70     push_up(y);
 71 }
 72 void Splay(int r,int goal)
 73 {
 74     push_down(r);
 75     while (pre[r] != goal)
 76     {
 77         if (pre[pre[r]] == goal)
 78         {
 79             push_down(pre[r]);
 80             push_down(r);
 81             Rotate(r,ch[pre[r]][0] == r);
 82         }
 83         else
 84         {
 85             int y = pre[r];
 86             int kind = (ch[pre[y]][1] == y);
 87             push_down(pre[y]);
 88             push_down(y);
 89             push_down(r);
 90             if (ch[y][kind] == r)
 91             {
 92                 Rotate(y,!kind);
 93                 Rotate(r,!kind);
 94             }
 95             else
 96             {
 97                 Rotate(r,kind);
 98                 Rotate(r,!kind);
 99             }
100         }
101     }
102     push_up(r);
103     if (goal == 0)
104         root = r;
105 }
106 int Get_kth(int r,int k)
107 {
108     push_down(r);
109     int t = siz[ch[r][0]] + 1;
110     if (k == t)
111         return r;
112     if (k >= t)
113         return Get_kth(ch[r][1],k-t);
114     else
115         return Get_kth(ch[r][0],k);
116 }
117 void Reverse(int u,int v)
118 {
119     Splay(Get_kth(root,u),0);
120     Splay(Get_kth(root,v+2),root);
121     update_rev(ch[ch[root][1]][0]);
122     push_up(ch[root][1]);
123     push_up(root);
124 }
125 void dfs(int r)
126 {
127     if (!r)
128         return;
129     push_down(r);
130     dfs(ch[r][0]);
131     if (r != -1 && key[r] != -1)        //-1设置的虚节点 
132         printf("%d
",key[r]);
133     dfs(ch[r][1]);
134 }
135 int main(void)
136 {
137     #ifndef ONLINE_JUDGE
138         freopen("in.txt","r",stdin);
139     #endif
140     while (~scanf ("%d%d",&n,&m))
141     {
142         init();
143         for (int i = 0; i < m; i++)
144         {
145             int u,v;
146             scanf ("%d%d",&u,&v);
147             Reverse(u,n);
148             Reverse(u,u+n-v-1);
149         }
150         dfs(root);
151     }
152     return 0;
153 }