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  1. /*
  2.  *    J1K7_7
  3.  *
  4.  *    You can use my contents on a Creative Commons - Attribution 4.0 International - CC BY 4.0 License.  XD 
  5.  *    - JASKAMAL KAINTH
  6.  */
  7. #include <iostream>
  8. #include <sstream>
  9. #include <fstream>
  10. #include <string>
  11. #include <vector>
  12. #include <deque>
  13. #include <queue>
  14. #include <stack>
  15. #include <set>
  16. #include <cstring>
  17. #include <cassert>
  18. #include <list>
  19. #include <map>
  20. #include <unordered_map>
  21. #include <iomanip>
  22. #include <algorithm>
  23. #include <functional>
  24. #include <utility>
  25. #include <bitset>
  26. #include <cmath>
  27. #include <cstdlib>
  28. #include <ctime>
  29. #include <cstdio>
  30. #include <limits>
  31. using namespace std;
  32. typedef long long          ll;
  33. typedef unsigned long long ull;
  34. typedef long double        ld;
  35. typedef pair<int,int>      pii;
  36. typedef pair<ll,ll>        pll;
  37. typedef vector<int>        vi;
  38. typedef vector<long long>  vll;
  39. #define left(x) 		   (x << 1)
  40. #define right(x) 		   (x << 1) + 1
  41. #define mid(l, r) 	       ((l + r) >> 1)
  42. #define mp                 make_pair
  43. #define pb                 push_back
  44. #define all(a)             a.begin(),a.end()
  45. #define ff                  first
  46. #define ss                 second
  47. const int maxn = 3e5+7;
  48. int n; // number of nodes
  49.  
  50. vector<int> G[maxn];
  51. int low[maxn], disc[maxn] , parent[maxn] , vis[maxn];
  52. vector<pair<int,int> > bedge; // all bridge edges 
  53. int timer;
  54. vector<int> Btree[maxn]; 
  55.  
  56. int rankN[maxn];
  57. int parentN[maxn];
  58. inline void make_set()
  59. {
  60. 	for(int i = 0; i < n; i++)
  61. 		parentN[i] = rankN[i] = i;  
  62. }
  63. inline int find_set(int u)
  64. {
  65. 	if(parentN[u] != u )
  66. 		parentN[u] = find_set(parentN[u]);
  67. 	return parentN[u];
  68. }
  69. inline void union_set(int u,int v)
  70. {
  71. 	int pu = find_set(u);
  72. 	int pv = find_set(v);
  73. 	if(pu == pv)
  74. 		return ;
  75. 	if(rankN[pu] > rankN[pv])
  76. 	{
  77. 		parentN[pv] = pu;  
  78. 	}
  79. 	else
  80. 	{
  81. 		parentN[pu] = pv;
  82. 		if(rankN[pu] == rankN[pv])
  83. 			rankN[pv]++;
  84. 	}
  85. }
  86. inline void init_bridge_tree()
  87. {
  88. 	make_set();
  89. 	timer = 0;
  90. 	for(int i = 0; i < maxn; i++)
  91. 	{
  92. 		low[i] = disc[i] = vis[i] = 0;
  93. 		parent[i] = -1;
  94. 	}
  95. }
  96. /* Mark all the bridges */
  97. inline void mark_bridges(int u)
  98. {
  99. 	vis[u] = 1;
  100. 	disc[u] = low[u] = timer++;
  101. 	for(int &v: G[u])
  102. 	{
  103. 		if(!vis[v])
  104. 		{
  105. 			parent[v] = u;
  106. 			mark_bridges(v);
  107. 			low[u] = min(low[u],low[v]);
  108. 			if(low[v] > disc[u])
  109. 			{
  110. 				bedge.push_back(mp(u,v));
  111. 			}
  112. 			else
  113. 			{
  114. 				union_set(u,v);
  115. 			}
  116. 		}
  117. 		else if(parent[u] != v)
  118. 		{
  119. 			low[u] = min(low[u],disc[v]);
  120. 		}
  121. 	}
  122. }
  123. inline void make_tree()
  124. {
  125. 	init_bridge_tree();
  126. 	mark_bridges(0); // mark all the bridges
  127. 	for(auto &i: bedge) // atmose n-1 bridge edges.
  128. 	{
  129. 		int pu = find_set(i.ff);
  130. 		int pv = find_set(i.ss);
  131. 		if(pu != pv)
  132. 		{
  133. 			Btree[pu].push_back(pv);
  134. 			Btree[pv].push_back(pu);
  135. 		}
  136. 	}
  137. }
  138. const int MAXN = 3e5+7; 
  139. const int MAXLOG = 20; 
  140.  
  141. int P[MAXN][MAXLOG]; // initially all -1
  142. int d[MAXN];
  143. void dfs1(int v,int p = -1){
  144. 	P[v][0] = p;
  145. 	if(p + 1)
  146. 		d[v] = d[p] + 1;
  147. 	for(int i = 1;i < MAXLOG;i ++)
  148. 		if(P[v][i-1] + 1)
  149. 			P[v][i] = P[P[v][i-1]][i-1];
  150. 	for(auto u : Btree[v])
  151. 		if(p - u)
  152. 			dfs1(u,v);
  153. }
  154. void process3(int N  = n)
  155. {
  156. 	int i, j;
  157. 	for (i = 0; i < N; i++)
  158. 		for (j = 0; 1 << j < N; j++)
  159. 			P[i][j] = -1;
  160. 	for (j = 1; 1 << j < N; j++)
  161. 		for (i = 0; i < N; i++)
  162. 			if (P[i][j - 1] != -1)
  163. 				P[i][j] = P[P[i][j - 1]][j - 1];
  164. }
  165.  
  166. int query(int p, int q)
  167. {
  168. 	int tmp, log, i;
  169. 	if (d[p] < d[q])
  170. 		tmp = p, p = q, q = tmp;
  171. 	for (log = 1; 1 << log <= d[p]; log++);
  172. 	log--;
  173. 	for (i = log; i >= 0; i--)
  174. 		if (d[p] - (1 << i) >= d[q])
  175. 			p = P[p][i];
  176. 	if (p == q)
  177. 		return p;
  178. 	for (i = log; i >= 0; i--)
  179. 		if (P[p][i] != -1 && P[p][i] != P[q][i])
  180. 			p = P[p][i], q = P[q][i];
  181. 	return P[p][0];
  182. }
  183.  
  184. int dist(int u , int  v)
  185. {
  186.     int l =query( u , v);
  187.     return ( d[u] + d[v] - 2 * d[l] );
  188. }
  189. int main()
  190. {
  191.     ios_base::sync_with_stdio(false); cin.tie(0);
  192.  
  193. 	int  m , q; cin >> n >> m >> q;
  194.  
  195. 	init_bridge_tree();
  196. 	for(int i = 0; i < m ; i++)
  197. 	{
  198. 		int u , v; cin >> u >> v;
  199. 		u--; v--;
  200. 		G[u].pb(v);
  201. 		G[v].pb(u);
  202. 	}
  203.  
  204. 	make_set();
  205. 	make_tree();
  206. 	process3();
  207. 	dfs1(find_set(0));
  208.  
  209. 	while(q--)
  210. 	{
  211. 		int a , b; cin >> a >> b;  
  212. 		a--; b--;
  213. 		int pi = find_set(a);
  214. 		int pj = find_set(b);
  215. 		if(pi == pj )
  216. 		{
  217. 			cout << "0" << "\n";  
  218. 		}
  219. 		else
  220. 		{
  221. 			cout << dist(pi,pj) << "\n";  
  222. 		}
  223. 	}
  224. 	return 0;
  225. }
  226.  
  227.  
Success #stdin #stdout 0s 42144KB
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https://ideone.com/fWIKgU
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
secret

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