cf 1601B Frog Traveler Codeforces Round 751 (Div. 1) bfs，合并向上后的点的区间（TODO 01BFS的方法 线段树的方法）

 

Problem - 1601B - Codeforces

 

TODO 01BFS的方法

TODO 题解线段树的方法是？ （可以用线段树记录向上后的点的区间？比下面代码不断用vector<pair<int,int> > 和合并方便和不容易写错一点？）

 

 

BFS

然后每次上升可以的范围是一个区间，然后每次都遍历这个区间的所有点，那么超时。用set等方式，合并这些区间，之前没遍历过的范围才更新（加入BFS需要遍历的队列里）。但是区间的更新特别容易写错……

 

我的代码 和 造数据

  1 /**
  2 记录两个vis？
  3 1. 向上到达的区间
  4 2. 下滑到的点
  5 **/
  6 //#include <bits/stdc++.h>
  7 #include <cstdio>
  8 #include <cstdlib>
  9 #include <cstring>
 10 #include <cmath>
 11 #include <cstdbool>
 12 #include <string>
 13 #include <algorithm>
 14 #include <iostream>
 15 #include <sstream>
 16 #include <ctime>
 17 #include <stack>
 18 #include <vector>
 19 #include <queue>
 20 #include <set>
 21 #include <map>
 22 #include <array>
 23 #include <bitset>
 24 using namespace std;
 25 #define LL long long
 26 #define ULL unsigned long long
 27  
 28 const LL mod_1=1e9+7;
 29 const LL mod_2=998244353;
 30  
 31 const double eps_1=1e-5;
 32 const double eps_2=1e-10;
 33  
 34 const int maxn=3e5+10;
 35  
 36 set<pair<int,int> > s;
 37 set<pair<int,int> >::iterator it;
 38 vector<pair<int,int> > need_del;
 39  
 40 int q[maxn],hap[maxn],a[maxn],b[maxn],step[maxn],pre[maxn],reach[maxn];
 41 bool vis_down[maxn];
 42  
 43 int n,i,head,tail,d,x,y,L,R,pre_x,nex_y,old_y;
 44  
 45 ///test
 46 LL TEST_hap_Z=0, TEST_hap_interval=0;
 47 bool visz[maxn];
 48 bool print_test=0;
 49  
 50 void add_q(int Z1, int Z2)
 51 {
 52     int Z, cur_pos;
 53     if (print_test)
 54         TEST_hap_Z++;
 55     if (print_test)
 56         printf("Z range %d %d\n",Z1,Z2);
 57     for (Z=Z1;Z<=Z2;Z++)
 58     {
 59         if (print_test)
 60         {
 61             if (visz[Z])
 62             {
 63                 printf("Z overlap\n");
 64                 exit(1);
 65             }
 66             visz[Z]=1;
 67         }
 68  
 69         cur_pos = Z+b[Z];
 70  
 71         if (!vis_down[cur_pos])
 72         {
 73             vis_down[cur_pos]=1;
 74             tail++;
 75             q[tail]=cur_pos;
 76             step[cur_pos]=step[d]+1;
 77             pre[cur_pos]=d;
 78             reach[cur_pos]=Z;
 79         }
 80     }
 81 }
 82  
 83 void print(int D)
 84 {
 85     if (D==n)
 86         return;
 87     print(pre[D]);
 88     printf("%d ",reach[D]);
 89 }
 90  
 91 void test_print()
 92 {
 93     exit(0);
 94     cout<<"TEST_hap_Z="<<TEST_hap_Z<<" TEST_hap_interval="<<TEST_hap_interval<<endl;
 95 }
 96  
 97 int main()
 98 {
 99     if (print_test)
100         memset(visz,0,sizeof(visz));
101  
102     memset(hap,0,sizeof(hap));
103     scanf("%d",&n);
104     for (i=1;i<=n;i++)
105         scanf("%d",&a[i]);
106     for (i=1;i<=n;i++)
107         scanf("%d",&b[i]);
108     b[0]=0;
109  
110     memset(vis_down,0,sizeof(vis_down));
111     memset(step,0xff,sizeof(step));
112     head=0,tail=1;
113     vis_down[n]=1,step[n]=0,q[1]=n;
114     while (head<tail)
115     {
116         ///不能先添加一个相同的，再删除一个相同的。那么本来要添加的就没有了
117         for (auto pa : need_del)
118         {
119             if (print_test)
120                 cout<<"need erase "<<pa.first<<" "<<pa.second<<endl;
121             s.erase(pa);
122         }
123  
124         need_del.clear();
125  
126         if (print_test)
127         {
128             for (auto auto_set_pair:s)
129                 cout<<auto_set_pair.first<<" "<<auto_set_pair.second<<" ; ";
130             cout<<endl;
131         }
132  
133         head++;
134         d = q[head];
135         R = d;
136         L = d - a[ d ];
137  
138  
139         R--;
140         if (L>R)
141             continue;
142  
143  
144         ///after jump up : range [L,R]
145  
146         if (L==0)
147         {
148             printf("%d\n",step[d]+1);
149             print(d);
150             printf("0\n");
151             if (print_test)
152                 test_print();
153             return 0;
154         }
155  
156         ///>
157         it = upper_bound( s.begin(), s.end(), make_pair(L, R) );   ///v
158  
159         if (s.size()==0)
160         {
161             s.insert( make_pair(L, R) );
162             add_q(L, R);
163             continue;
164         }
165         else if (it==s.begin())
166         {
167             x = L;
168             y = s.begin()->second;
169             add_q(L, s.begin()->first-1);
170  
171             if (R<=y)
172             {
173                 need_del.push_back( *it );
174                 s.insert(make_pair(x, y));
175                 continue;
176             }
177         }
178         //else if (it==s.end())
179         else
180         {
181             it--;
182             x = it->first;
183             y = it->second;
184             if (R<=y)
185                 continue;
186         }
187  
188         pre_x = x;
189  
190         while (R>y) ///
191         {
192             if (print_test)
193                 TEST_hap_interval++;
194  
195             old_y = y;
196  
197             need_del.push_back( *it );
198  
199             it = ++it;
200             if (it!=s.end())
201             {
202                 x = it->first;  ///new_interval x
203                 y = it->second; ///new_interval y
204             }
205             if (it==s.end() || x>R)
206             {
207                 add_q(old_y+1, R);
208                 s.insert(make_pair(pre_x, R));
209                 continue;
210             }
211  
212             add_q(old_y+1, x-1);
213         }
214  
215         s.insert(make_pair(pre_x, y));
216     }
217  
218     printf("-1\n");
219  
220     if (print_test)
221         test_print();
222  
223     return 0;
224 }
225 /**
226 1
227 1
228 0
229  
230 ======
231  
232 5
233 1 1 1 1 1
234 2 2 2 1 0
235  
236 ======
237  
238 5
239 2 2 2 2 2
240 1 1 1 1 0
241  
242 =======
243  
244 excel
245  
246 10
247  
248 1    0    0    3    5    0    4    6    3    1
249 7    0    1    0    0    1    0    3    0    0
250  
251  
252  
253 ======
254  
255  
256  
257 5
258 0 2 1 4 1
259 2 0 0 1 0
260  
261  
262 5
263 1 2 3 1 0
264 2 2 1 0 0
265  
266  
267 5
268 1 2 0 0 5
269 0 2 1 0 0
270  
271  
272 5
273 1 2 2 1 4
274 1 0 0 1 0
275  
276  
277  
278 ======
279  
280 Z overlap
281  
282  
283  
284 100
285 0 0 3 4 1 5 1 5 3 5 8 3 4 11 11 9 8 0 9 8 4 8 16 24 15 0 0 6 10 17 9 6 32 34 28 1 12 31 15 16 15 18 8 44 9 36 28 33 42 1 28 49 15 36 48 8 2 20 26 37 18 29 29 7 16 32 30 9 19 35 59 58 65 32 42 7 14 29 37 73 6 37 44 21 56 61 66 75 37 44 55 74 56 49 77 66 68 72 5 12
286 19 56 63 56 11 47 74 35 38 33 69 84 55 13 58 15 43 11 27 34 22 45 43 41 58 68 2 28 21 27 27 22 54 50 10 10 19 6 36 48 38 53 17 56 5 47 41 31 47 33 25 24 35 28 39 8 19 10 33 16 33 9 12 30 1 5 33 25 8 23 19 20 3 26 1 11 18 6 19 4 18 16 4 8 1 8 7 7 6 7 2 2 1 0 3 0 3 0 1 0
287  
288  
289  
290  
291 15
292 1 1 0 4 5 0 0 5 4 10 3 8 3 3 1
293 1 3 5 0 10 2 1 0 2 0 0 1 2 0 0
294  
295  
296  
297 ======
298  
299  
300  
301 15
302 1 0 1 1 3 3 5 1 6 2 1 4 10 9 1
303 9 4 7 8 8 5 0 0 5 3 4 0 0 1 0
304  
305  
306 15
307 1 1 2 4 1 2 6 1 0 6 11 3 0 6 14
308 8 2 1 4 2 0 4 5 5 5 3 3 0 0 0
309  
310  
311 15
312 0 2 0 4 5 5 4 0 6 1 10 12 5 13 4
313 9 10 0 5 4 8 8 7 4 1 1 2 2 1 0
314  
315  
316 15
317 1 1 0 4 5 0 0 5 4 10 3 8 3 3 1
318 1 3 5 0 10 2 1 0 2 0 0 1 2 0 0
319  
320  
321 15
322 1 0 0 1 3 3 7 1 3 10 4 2 13 3 3
323 10 3 10 7 5 9 1 7 3 4 4 3 2 0 0
324  
325  
326 15
327 1 1 1 2 1 5 5 6 4 2 5 4 5 12 3
328 9 9 10 10 9 2 1 5 6 4 2 3 2 1 0
329  
330  
331 15
332 0 1 1 0 1 1 6 7 5 4 3 4 10 1 13
333 1 9 12 2 10 2 1 4 2 2 2 3 1 0 0
334  
335  
336 15
337 1 1 1 0 3 3 6 7 0 8 4 1 1 8 2
338 6 13 5 3 10 3 5 3 3 1 0 2 0 0 0
339  
340  
341 15
342 1 1 3 1 3 4 0 5 3 7 6 6 4 4 4
343 9 10 10 4 3 2 8 7 2 0 2 3 0 0 0
344  
345  
346 15
347 1 1 2 4 0 5 5 1 5 2 6 8 1 12 7
348 0 12 10 10 6 0 1 5 0 0 3 3 0 0 0
349  
350  
351  
352 **/

 

 

 

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 #define LL long long
 4 #define ULL unsigned long long
 5 
 6 const LL mod_1=1e9+7;
 7 const LL mod_2=998244353;
 8 
 9 const double eps_1=1e-5;
10 const double eps_2=1e-10;
11 
12 const int maxn=2e5+10;
13 
14 void work()
15 {
16     int n=15;    ///5 20 50
17     //int n=3e5;
18     int i;
19     printf("%d\n",n);
20     for (i=1;i<=n;i++)
21         printf("%d ", rand()%(i+1) );
22     printf("\n");
23     for (i=1;i<=n;i++)
24         printf("%d ", rand()%(n-i+1) );
25 }
26 
27 int main()
28 {
29     //work();
30     srand(time(NULL));
31 
32     int times=10;
33     while (times--)
34     {
35         work();
36         printf("\n\n\n");
37     }
38 
39     return 0;
40 }
41 /*
42 5
43 0 2 1 4 1
44 2 0 0 1 0
45 
46 
47 5
48 1 2 3 1 0
49 2 2 1 0 0
50 
51 
52 5
53 1 2 0 0 5
54 0 2 1 0 0
55 
56 
57 5
58 1 2 2 1 4
59 1 0 0 1 0
60 */

 

posted @ 2024-04-25 11:33  congmingyige  阅读(6)  评论(0)  编辑  收藏  举报