hdu 3487 Play with Chain (Splay Tree easy)

acm.hdu.edu.cn/showproblem.php?pid=3487
　　再来一道Splay Tree的简单题，因为只用到两个基本操作，剪接和反转。虽说是简单题，可是我对细节稍有疏忽，所以我wa了几次。问题出在延迟标记的更新上，可能是半夜打代码的缘故，头脑有点不灵活，从而导致这种不容易debug出问题的错误，以后要多加注意这样的小问题！
AC代码：
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  1 #include <cstdio>
  2 #include <cstdlib>
  3 #include <cstring>
  4 #include <algorithm>
  5 
  6 using namespace std;
  7 const int inf = 0x7f7f7f7f;
  8 
  9 bool pnt;
 10 struct Node {
 11     int key, cnt;
 12     bool rev;
 13     Node *c[2], *p;
 14 
 15     Node(int _key = 0, int _cnt = 0) {
 16         cnt = _cnt;
 17         key = _key;
 18         rev = false;
 19         c[0] = c[1] = p = NULL;
 20     }
 21 } *Null, *Root;
 22 
 23 void up(Node *rt) {
 24     rt->cnt = rt->c[0]->cnt + rt->c[1]->cnt + 1;
 25 }
 26 
 27 void down(Node *rt) {
 28     if (rt->rev) {
 29         Node *ls = rt->c[0], *rs = rt->c[1];
 30 
 31         if (ls != Null) {
 32             swap(ls->c[0], ls->c[1]);
 33             ls->rev = !ls->rev;
 34         }
 35         if (rs != Null) {
 36             swap(rs->c[0], rs->c[1]);
 37             rs->rev = !rs->rev;
 38         }
 39         rt->rev = false;
 40     }
 41 }
 42 
 43 void rotate(Node *x, bool right) {
 44     Node *y = x->p;
 45 
 46     down(y);
 47     down(x);
 48     y->c[!right] = x->c[right];
 49     if (x->c[right] != Null) {
 50         x->c[right]->p = y;
 51     }
 52     x->p = y->p;
 53     if (y->p != Null) {
 54         if (y->p->c[0] == y) y->p->c[0] = x;
 55         else y->p->c[1] = x;
 56     }
 57     x->c[right] = y;
 58     y->p = x;
 59 
 60     up(y);
 61     if (y == Root) Root = x;
 62 }
 63 
 64 void splay(Node *x, Node *f) {
 65     down(x);
 66     while (x->p != f) {
 67         if (x->p->p == f) {
 68             if (x->p->c[0] == x) rotate(x, 1);
 69             else rotate(x, 0);
 70         } else {
 71             Node *y = x->p, *z = y->p;
 72 
 73             if (z->c[0] == y) {
 74                 if (y->c[0] == x) {
 75                     rotate(y, 1);
 76                     rotate(x, 1);
 77                 } else {
 78                     rotate(x, 0);
 79                     rotate(x, 1);
 80                 }
 81             } else {
 82                 if (y->c[0] == x) {
 83                     rotate(x, 1);
 84                     rotate(x, 0);
 85                 } else {
 86                     rotate(y, 0);
 87                     rotate(x, 0);
 88                 }
 89             }
 90         }
 91     }
 92 
 93     up(x);
 94 }
 95 
 96 void inTra(Node *rt) {
 97     if (rt == Null) {
 98         return ;
 99     }
100     down(rt);
101     inTra(rt->c[0]);
102     if (rt->key != inf){
103         if (!pnt) pnt = true;
104         else putchar(' ');
105         printf("%d", rt->key);
106     }
107     inTra(rt->c[1]);
108 }
109 
110 void initSplay() {
111     Null = new Node();
112     Root = new Node(inf, 1);
113 
114     Root->p = Root->c[0] = Null;
115     Root->c[1] = new Node(inf, 1);
116     Root->c[1]->p = Root;
117     Root->c[1]->c[0] = Root->c[1]->c[1] = Null;
118     up(Root);
119 }
120 
121 void insSplay(int x) {
122     Node *tmp = new Node(x, 1);
123 
124     tmp->c[1] = Root->c[1];
125     Root->c[1]->p = tmp;
126     Root->c[1] = tmp;
127     tmp->p = Root;
128     tmp->c[0] = Null;
129 
130     splay(tmp, Null);
131 }
132 
133 Node *getNode(int pos) {
134     Node *p = Root;
135 
136     pos++;
137     while (true) {
138         down(p);
139 
140         int cnt = p->c[0]->cnt;
141 
142 //        printf("pos %d  cnt %d\n", pos, cnt);
143         if (pos == cnt + 1) {
144             return p;
145         } else if (pos <= cnt) {
146             p = p->c[0];
147         } else {
148             pos -= cnt + 1;
149             p = p->c[1];
150         }
151     }
152 }
153 
154 void cutSeg(int l, int r, int pos) {
155     Node *pl = getNode(l - 1);
156     splay(pl, Null);
157     Node *pr = getNode(r + 1);
158     splay(pr, pl);
159 
160 //    inTra(Root);
161 //    puts("!!!");
162 
163     // cut segment
164     Node *tmp = pr->c[0];
165 
166     down(tmp);
167     pr->c[0] = Null;
168     splay(pr, Null);
169     // insert segment
170 //    printf("pos %d\n", pos);
171 //    inTra(Root);
172 //    puts("~~~");
173     pl = getNode(pos);
174     splay(pl, Null);
175     pr = getNode(pos + 1);
176     splay(pr, pl);
177 //    puts("cut??");
178 
179     pr->c[0] = tmp;
180     tmp->p = pr;
181     splay(tmp, Null);
182 }
183 
184 void reverse(int l, int r) {
185     Node *pl = getNode(l - 1);
186     splay(pl, Null);
187     Node *pr = getNode(r + 1);
188     splay(pr, pl);
189 
190     pr = pr->c[0];
191     down(pr);
192     pr->rev = true;
193     swap(pr->c[0], pr->c[1]);
194     splay(pr, Null);
195 }
196 
197 void build(int n) {
198     initSplay();
199     for (int i = 1; i <= n; i++) {
200         insSplay(i);
201     }
202 }
203 
204 void process(int m) {
205     char buf[5];
206     int l, r, pos;
207 
208     while (m--) {
209         scanf("%s", buf);
210         if (buf[0] == 'C') {
211             scanf("%d%d%d", &l, &r, &pos);
212             if (l > r) swap(l, r);
213             cutSeg(l, r, pos);
214 //            puts("cut~");
215         } else {
216             scanf("%d%d", &l, &r);
217             if (l > r) swap(l, r);
218             reverse(l, r);
219 //            puts("flip~");
220         }
221     }
222 }
223 
224 void delSplay(Node *rt) {
225     if (rt == Null) {
226         return ;
227     } else {
228         delSplay(rt->c[0]);
229         delSplay(rt->c[1]);
230         delete rt;
231     }
232 }
233 
234 int main() {
235     int n, m;
236 
237 //    freopen("in", "r", stdin);
238 //    freopen("out", "w", stdout);
239     while (~scanf("%d%d", &n, &m) && (n >= 0 || m >= 0)) {
240         build(n);
241 //        inTra(Root);
242 //        puts("built!");
243         process(m);
244 //        puts("processed!");
245         pnt = false;
246         inTra(Root);
247         puts("");
248         delSplay(Root);
249         delete Null;
250     }
251 
252     return 0;
253 }
——written by Lyon