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  1. #include <bits/stdc++.h>
  2. #define vi vector<int>
  3. #define pb push_back
  4. #define fo(i, n) for(i=0; i<n; i++)
  5. using namespace std;
  6. const int N=40011,M=100011;
  7. int BLOCK;
  8. struct node{
  9. 	int l, r, i, sp, ans;
  10. }Q[M];
  11. int lvl[N], p[N][16], st[N], en[N], id[2*N], occ[N], ans, w[N];
  12. map<int, int> HASH;
  13. int cnt[N];
  14. vi g[N];
  15. int ti;
  16. bool f(node a, node b){
  17. 	if (a.l/BLOCK != b.l/BLOCK)
  18. 		return a.l < b.l;
  19. 	return a.r < b.r;
  20. }
  21. bool gg(node a, node b){
  22. 	return a.i < b.i;
  23. }
  24. void dfs(int u, int p){
  25.  
  26. 	st[u] = ++ti;
  27. 	id[ti] = u;
  28. 	int v;
  29. 	for(auto v: g[u]){
  30. 		if (v == p)
  31. 			continue;
  32. 		lvl[v] = lvl[u]+1;
  33. 		::p[v][0] = u;
  34. 		dfs(v, u);
  35. 	}
  36. 	en[u] = ++ti;
  37. 	id[ti] = u;
  38. }
  39. int lca(int u, int v){
  40. 	int lg, i;
  41. 	for (lg = 0; (1<<lg) <= lvl[u]; lg++);
  42. 	lg--;
  43. 	for(i=lg; i>=0; i--)
  44. 		if ( lvl[u] - (1<<i) >= lvl[v])
  45. 			u = p[u][i];
  46. 	if (u == v)
  47. 		return u;
  48. 	for(i = lg; i >= 0; i--){
  49. 		if (p[u][i] != -1 && p[u][i] != p[v][i])
  50. 			u = p[u][i], v = p[v][i];
  51. 	}
  52. 	return p[u][0];
  53. }
  54. void add(int node){
  55. 	occ[node]++;
  56. 	cnt[w[node]]++;
  57. 	if (occ[node] == 2){
  58. 		cnt[w[node]] -= 2;
  59. 		if (cnt[w[node]] == 0)
  60. 			ans--;
  61. 	}
  62. 	else if (cnt[w[node]] == 1) ans++;
  63. }
  64. void del(int node){
  65. 	int wt = w[node];
  66. 	occ[node]--;
  67.  
  68. 	if (occ[node] == 1){
  69. 		cnt[wt]++;
  70. 		if (cnt[wt] == 1)
  71. 			ans++;
  72. 		return;
  73. 	}
  74. 	cnt[wt]--;
  75. 	if (cnt[wt] == 0) ans--;
  76. }
  77. int main() {
  78. 	ios_base::sync_with_stdio(false);
  79. 	int n, m, i, j, u, v;
  80. 	ans = ti = 0;
  81. 	cin>>n>>m;
  82. 	BLOCK = sqrt(n);
  83. 	int no = 0;
  84. 	HASH.clear();
  85. 	fo(i, n){
  86. 		cin>>w[i+1];
  87. 		if (HASH.find(w[i+1]) == HASH.end())
  88. 			HASH[w[i+1]] = ++no;
  89. 		w[i+1] = HASH[w[i+1]];
  90.  
  91. 	}
  92. 	fo(i, n-1){
  93. 		cin>>u>>v;
  94. 		g[u].pb(v);
  95. 		g[v].pb(u);
  96. 	}
  97. 	lvl[1] = 0;
  98. 	memset(cnt, 0, sizeof(cnt));
  99. 	memset(occ, 0, sizeof(occ));
  100. 	memset(p, -1, sizeof(p));
  101. 	dfs(1, 0);
  102. 	for(i=1; i<16; i++)
  103. 	for(j=1; j<=n; j++)
  104. 		if( p[j][i-1] != -1)
  105. 			p[j][i] = p[p[j][i-1]][i-1];
  106. 	fo(i, m){
  107. 		Q[i].i = i;
  108. 		Q[i].sp = -1;
  109. 		cin>>u>>v;
  110. 		if (lvl[u] < lvl[v])
  111. 			swap(u, v);
  112. 		int w = lca(u, v);
  113. 		if (w == v){
  114. 			Q[i].l = st[v];
  115. 			Q[i].r = st[u]+1;
  116. 		}else{
  117. 			if (st[v] > en[u]){
  118. 				Q[i].l = en[u];
  119. 				Q[i].r = st[v]+1;
  120. 			}
  121. 			else{
  122. 				Q[i].l = en[v];
  123. 				Q[i].r = st[u]+1;
  124. 			}
  125. 			// Special case: We have to consider 'w' separately.
  126. 			Q[i].sp = w;
  127. 		}
  128. 	}
  129. 	sort(Q, Q+m, f);
  130. 	int currL = 0, currR = 0, L, R;
  131. 	fo(i, m){
  132. 		L = Q[i].l, R = Q[i].r;
  133. 		while (currL < L){
  134.  
  135. 			del(id[currL]);
  136. 			currL++;
  137. 		}
  138. 		while (currL > L){
  139. 			add(id[currL-1]);
  140. 			currL--;
  141. 		}
  142. 		while (currR < R){
  143. 			add(id[currR]);
  144. 			currR++;
  145. 		}
  146. 		while (currR > R){
  147. 			del(id[currR-1]);
  148. 			currR--;
  149. 		}
  150. 		Q[i].ans = ans;
  151. 		if (Q[i].sp != -1){
  152. 			if (cnt[w[Q[i].sp]] == 0)				
  153. 				Q[i].ans = ans+1;
  154. 		}
  155. 	}
  156. 	sort(Q, Q+m, gg);
  157. 	fo(i, m)
  158. 		cout<<Q[i].ans<<endl;
  159.  
  160. 	return 0;
  161. }
Success #stdin #stdout 0s 9592KB
comments (?)
stdin 
8 2
105 2 9 3 8 5 7 7
1 2        
1 3
1 4
3 5
3 6
3 7
4 8
2 5
7 8
stdout 
4
4
https://ideone.com/aLS5Yx
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
secret

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