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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. #define gc getchar_unlocked
  4. #define fo(i,n) for(i=0;i<n;i++)
  5. #define Fo(i,k,n) for(i=k;k<n?i<n:i>n;k<n?i+=1:i-=1)
  6. #define ll long long
  7. #define si(x)	scanf("%d",&x)
  8. #define sl(x)	scanf("%lld",&x)
  9. #define ss(s)	scanf("%s",s)
  10. #define pi(x)	printf("%d\n",x)
  11. #define pl(x)	printf("%lld\n",x)
  12. #define ps(s)	printf("%s\n",s)
  13. #define pb push_back
  14. #define mp make_pair
  15. #define F first
  16. #define S second
  17. #define all(x) x.begin(), x.end()
  18. #define clr(x) memset(x, 0, sizeof(x))
  19. #define sortall(x) sort(all(x))
  20. #define tr(it, a) for(auto it = a.begin(); it != a.end(); it++)
  21. #define PI 3.1415926535897932384626
  22. typedef pair<int, int>	pii;
  23. typedef pair<ll, ll>	pl;
  24. typedef vector<int>		vi;
  25. typedef vector<ll>		vl;
  26. typedef vector<pii>		vpii;
  27. typedef vector<pl>		vpl;
  28. typedef vector<vi>		vvi;
  29. typedef vector<vl>		vvl;
  30. int mpow(int base, int exp); 
  31. void ipgraph(int m);
  32. void dfs(int u, int par);
  33. const int mod = 1000000007;
  34. const int N = 2e5+1, M = N;
  35. //=======================
  36.  
  37. vi g[N];
  38. int a[N], p[N], v[N];
  39. int sum[N], id[N];
  40. map<int,int> cnt[N];
  41. int ans = 0;
  42.  
  43. int main()
  44. {
  45. 	ios_base::sync_with_stdio(false);
  46. 	cin.tie(NULL);
  47. 	int i,n,k,j;
  48. 	cin >> n;
  49. 	Fo(i, 1, n+1){
  50. 		id[i] = i;
  51. 		cin >> p[i] >> v[i];
  52. 		if(p[i]>0)
  53. 			g[p[i]].pb(i);
  54. 	}
  55. 	dfs(1, 0);
  56. 	cout << ans << endl;
  57. 	return 0;
  58. } 
  59.  
  60. void dfs(int u, int par){
  61. 	for(int v:g[u]){
  62. 		if (v == par) continue;
  63. 		dfs(v, u);
  64. 		if(cnt[id[v]].size() > cnt[id[u]].size()) swap(id[u], id[v]);
  65. 	}
  66.  
  67. 	int &cur = sum[id[u]];
  68. 	for(int v:g[u]){
  69. 		if (v == par) continue;
  70. 		for(auto it: cnt[id[v]]){
  71. 			int col = it.F, no = it.S;
  72. 			int &val = cnt[id[u]][col];
  73. 			cur -= val;
  74. 			if(cur < 0) cur += mod;
  75. 			val = ((val+1) *1LL* (no+1))%mod;
  76. 			val -= 1;
  77. 			if(val < 0) val += mod;
  78. 			cur += val;
  79. 			if(cur >= mod) cur -= mod;
  80. 		}
  81. 	}
  82. 	ll add = cur;
  83. 	cnt[id[u]][v[u]] += 1+add;
  84. 	if(cnt[id[u]][v[u]] >= mod) cnt[id[u]][v[u]] -= mod;
  85. 	ans += 1+add;
  86. 	if(ans >= mod) ans -= mod;
  87. 	cur += 1+add;
  88. 	if(cur >= mod) cur -= mod;
  89. }
Success #stdin #stdout 0s 34032KB
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https://ideone.com/hKjPww
small to large trick
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
secret

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