oj.uz

Submission #416980

# Submission time Handle Problem Language Result Execution time Memory
416980 2021-06-03T09:26:10 Z aryan12 The Xana coup (BOI21_xanadu) C++17
100 / 100
 102 ms 28208 KB 
#include <bits/stdc++.h>
using namespace std;
#define int long long

const int N = 1e5 + 5;
vector<int> g[N];
int val[N];
int dp[N][2][2];

/*
dp[i][j][k] => currently in the ith node, the ith subtree is safe (except the last layer, maybe) 
j => current condition of the node (0 = off, 1 = on)
k => whether the parents value has been altered or not (0 = no, 1 = yes)
*/

void dfs(int node, int par) {
	if(g[node].size() == 1) {
		dp[node][val[node]][0] = 0;
		dp[node][1LL - val[node]][1] = 1;
		return;
	}
	vector<int> children[2];
	int sum0 = 0, sum1 = 0;
	for(int i = 0; i < g[node].size(); i++) {
		if(g[node][i] != par) {
			dfs(g[node][i], node);
			sum0 += dp[g[node][i]][0][0];
			sum1 += dp[g[node][i]][1][0];
			if(dp[g[node][i]][0][1] != INT_MAX) {
				children[0].push_back(dp[g[node][i]][0][1] - dp[g[node][i]][0][0]);
			}
			if(dp[g[node][i]][1][1] != INT_MAX) {
				children[1].push_back(dp[g[node][i]][1][1] - dp[g[node][i]][1][0]);
			}
		}
	}
	for(int i = 0; i < 2; i++) {
		sort(children[i].begin(), children[i].end());
	}
	/*cout << "node = " << node << "\n";
	cout << "sum0 = " << sum0 << ", sum1 = " << sum1 << "\n";
	for(int i = 0; i < 2; i++) {
		cout << "iteration = " << i << "\n";
		for(int j = 0; j < children[i].size(); j++) {
			cout << children[i][j] << " ";
		}
		cout << "\n";
	}*/
	int prev0 = sum0, prev1 = sum1;


/* if all the children have their cameras off */

	//Subpart 1: not to change the value of node
	dp[node][val[node]][0] = min(dp[node][val[node]][0], sum0);
	for(int i = 0; i < children[0].size(); i += 2) {
		if(i + 1 == children[0].size())
			break;
		sum0 += (children[0][i] + children[0][i + 1]);
		dp[node][val[node]][0] = min(dp[node][val[node]][0], sum0);
	}

	//Subpart 2: change the value of the node
	if(children[0].size() != 0) {
		sum0 = prev0 + children[0][0];
		dp[node][1LL - val[node]][0] = min(dp[node][1LL - val[node]][0], sum0);
	}
	for(int i = 1; i < children[0].size(); i += 2) {
		if(i + 1 == children[0].size())
			break;
		sum0 += (children[0][i] + children[0][i + 1]);
		dp[node][1LL - val[node]][0] = min(dp[node][1LL - val[node]][0], sum0);
	}


/* if all the children have their cameras on 
   Note: parent and node have to be tempered, so its reverse */

	
	//Subpart 1: not to change the value of node 
	if(children[1].size() != 0) {
		sum1 = prev1 + children[1][0] + 1;
		dp[node][val[node]][1] = min(dp[node][val[node]][1], sum1);
	}
	for(int i = 1; i < children[1].size(); i += 2) {
		if(i + 1 == children[1].size())
			break;
		sum1 += children[1][i] + children[1][i + 1];
		dp[node][val[node]][1] = min(dp[node][val[node]][1], sum1);
	}

	//Subpart 2: change the value of node
	sum1 = prev1 + 1;
	dp[node][1LL - val[node]][1] = sum1;
	for(int i = 0; i < children[1].size(); i += 2) {
		if(i + 1 == children[1].size())
			break;
		sum1 += children[1][i] + children[1][i + 1];
		dp[node][1LL - val[node]][1] = min(dp[node][1LL - val[node]][1], sum1);
	}
}

void Solve() {
	for(int i = 0; i < N; i++) {
		for(int j = 0; j < 2; j++) {
			for(int k = 0; k < 2; k++) {
				dp[i][j][k] = INT_MAX;
			}
		}
	}
	int n;
	cin >> n;
	for(int i = 1; i < n; i++) {
		int v, u;
		cin >> v >> u;
		g[v].push_back(u);
		g[u].push_back(v);
	}
	g[1].push_back(-1);
	for(int i = 1; i <= n; i++) {
		cin >> val[i];
	}
	dfs(1, -1);
	int ans = min(dp[1][0][0], dp[1][0][1]);
	if(ans == INT_MAX) {
		cout << "impossible\n";
	}
	else {
		cout << ans << "\n";
	}
	//cout << min(dp[1][0][0], dp[1][0][1]) << "\n";
	/*for(int i = 1; i <= n; i++) {
		for(int j = 0; j < 2; j++) {
			for(int k = 0; k < 2; k++) {
				cout << "dp[" << i << "][" << j << "][" << k << "] = " << dp[i][j][k] << "\n";
			}
			cout << "\n\n";
		}
		cout << "\n\n\n\n";
	}*/
}

int32_t main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	int t = 1;
	//cin >> t;
	while(t--) {
		Solve();
	}
	return 0;
}

Compilation message

xanadu.cpp: In function 'void dfs(long long int, long long int)':
xanadu.cpp:24:19: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   24 |  for(int i = 0; i < g[node].size(); i++) {
      |                 ~~^~~~~~~~~~~~~~~~
xanadu.cpp:56:19: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   56 |  for(int i = 0; i < children[0].size(); i += 2) {
      |                 ~~^~~~~~~~~~~~~~~~~~~~
xanadu.cpp:57:12: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   57 |   if(i + 1 == children[0].size())
      |      ~~~~~~^~~~~~~~~~~~~~~~~~~~~
xanadu.cpp:68:19: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   68 |  for(int i = 1; i < children[0].size(); i += 2) {
      |                 ~~^~~~~~~~~~~~~~~~~~~~
xanadu.cpp:69:12: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   69 |   if(i + 1 == children[0].size())
      |      ~~~~~~^~~~~~~~~~~~~~~~~~~~~
xanadu.cpp:85:19: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   85 |  for(int i = 1; i < children[1].size(); i += 2) {
      |                 ~~^~~~~~~~~~~~~~~~~~~~
xanadu.cpp:86:12: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   86 |   if(i + 1 == children[1].size())
      |      ~~~~~~^~~~~~~~~~~~~~~~~~~~~
xanadu.cpp:95:19: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   95 |  for(int i = 0; i < children[1].size(); i += 2) {
      |                 ~~^~~~~~~~~~~~~~~~~~~~
xanadu.cpp:96:12: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   96 |   if(i + 1 == children[1].size())
      |      ~~~~~~^~~~~~~~~~~~~~~~~~~~~

Subtask #1
5.0 / 5.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 5708 KB Output is correct
2 Correct 4 ms 5708 KB Output is correct
3 Correct 4 ms 5708 KB Output is correct
4 Correct 4 ms 5796 KB Output is correct
5 Correct 4 ms 5708 KB Output is correct

Subtask #2
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 5708 KB Output is correct
2 Correct 4 ms 5708 KB Output is correct
3 Correct 4 ms 5708 KB Output is correct
4 Correct 4 ms 5796 KB Output is correct
5 Correct 4 ms 5708 KB Output is correct
6 Correct 6 ms 5800 KB Output is correct
7 Correct 3 ms 5764 KB Output is correct
8 Correct 5 ms 5708 KB Output is correct
9 Correct 4 ms 5708 KB Output is correct
10 Correct 4 ms 5708 KB Output is correct
11 Correct 4 ms 5800 KB Output is correct
12 Correct 3 ms 5708 KB Output is correct
13 Correct 3 ms 5708 KB Output is correct
14 Correct 4 ms 5708 KB Output is correct
15 Correct 4 ms 5708 KB Output is correct
16 Correct 4 ms 5708 KB Output is correct

Subtask #3
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 84 ms 28064 KB Output is correct
2 Correct 91 ms 27760 KB Output is correct
3 Correct 82 ms 28168 KB Output is correct

Subtask #4
40.0 / 40.0

# Verdict Execution time Memory Grader output
1 Correct 76 ms 28048 KB Output is correct
2 Correct 79 ms 27844 KB Output is correct
3 Correct 80 ms 28208 KB Output is correct
4 Correct 84 ms 11228 KB Output is correct
5 Correct 99 ms 11692 KB Output is correct
6 Correct 96 ms 11932 KB Output is correct
7 Correct 4 ms 5836 KB Output is correct
8 Correct 24 ms 7844 KB Output is correct
9 Correct 90 ms 11608 KB Output is correct
10 Correct 102 ms 11716 KB Output is correct
11 Correct 83 ms 12808 KB Output is correct
12 Correct 93 ms 13196 KB Output is correct
13 Correct 90 ms 11792 KB Output is correct
14 Correct 82 ms 12172 KB Output is correct

Subtask #5
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 5708 KB Output is correct
2 Correct 4 ms 5708 KB Output is correct
3 Correct 4 ms 5708 KB Output is correct
4 Correct 4 ms 5796 KB Output is correct
5 Correct 4 ms 5708 KB Output is correct
6 Correct 6 ms 5800 KB Output is correct
7 Correct 3 ms 5764 KB Output is correct
8 Correct 5 ms 5708 KB Output is correct
9 Correct 4 ms 5708 KB Output is correct
10 Correct 4 ms 5708 KB Output is correct
11 Correct 4 ms 5800 KB Output is correct
12 Correct 3 ms 5708 KB Output is correct
13 Correct 3 ms 5708 KB Output is correct
14 Correct 4 ms 5708 KB Output is correct
15 Correct 4 ms 5708 KB Output is correct
16 Correct 4 ms 5708 KB Output is correct
17 Correct 84 ms 28064 KB Output is correct
18 Correct 91 ms 27760 KB Output is correct
19 Correct 82 ms 28168 KB Output is correct
20 Correct 76 ms 28048 KB Output is correct
21 Correct 79 ms 27844 KB Output is correct
22 Correct 80 ms 28208 KB Output is correct
23 Correct 84 ms 11228 KB Output is correct
24 Correct 99 ms 11692 KB Output is correct
25 Correct 96 ms 11932 KB Output is correct
26 Correct 4 ms 5836 KB Output is correct
27 Correct 24 ms 7844 KB Output is correct
28 Correct 90 ms 11608 KB Output is correct
29 Correct 102 ms 11716 KB Output is correct
30 Correct 83 ms 12808 KB Output is correct
31 Correct 93 ms 13196 KB Output is correct
32 Correct 90 ms 11792 KB Output is correct
33 Correct 82 ms 12172 KB Output is correct
34 Correct 3 ms 5708 KB Output is correct
35 Correct 3 ms 5708 KB Output is correct
36 Correct 3 ms 5708 KB Output is correct
37 Correct 3 ms 5708 KB Output is correct
38 Correct 4 ms 5852 KB Output is correct
39 Correct 4 ms 5708 KB Output is correct
40 Correct 4 ms 5752 KB Output is correct
41 Correct 4 ms 5860 KB Output is correct
42 Correct 4 ms 5708 KB Output is correct
43 Correct 4 ms 5708 KB Output is correct
44 Correct 4 ms 5812 KB Output is correct
45 Correct 84 ms 28100 KB Output is correct
46 Correct 87 ms 27812 KB Output is correct
47 Correct 77 ms 28136 KB Output is correct
48 Correct 68 ms 11204 KB Output is correct
49 Correct 89 ms 11696 KB Output is correct
50 Correct 81 ms 11816 KB Output is correct
51 Correct 4 ms 5836 KB Output is correct
52 Correct 26 ms 7808 KB Output is correct
53 Correct 93 ms 11608 KB Output is correct
54 Correct 95 ms 11732 KB Output is correct
55 Correct 81 ms 12816 KB Output is correct
56 Correct 84 ms 13152 KB Output is correct
57 Correct 73 ms 11816 KB Output is correct
58 Correct 81 ms 12200 KB Output is correct
59 Correct 24 ms 7716 KB Output is correct
60 Correct 70 ms 10948 KB Output is correct
61 Correct 79 ms 11540 KB Output is correct
62 Correct 85 ms 11696 KB Output is correct
63 Correct 79 ms 11708 KB Output is correct
64 Correct 98 ms 11680 KB Output is correct
65 Correct 60 ms 12100 KB Output is correct
66 Correct 62 ms 12100 KB Output is correct
67 Correct 53 ms 12984 KB Output is correct
68 Correct 53 ms 13068 KB Output is correct
69 Correct 50 ms 13104 KB Output is correct
70 Correct 53 ms 13084 KB Output is correct