Submission #303975

#	Time	Username	Problem	Language	Result	Execution time	Memory
303975		peuch	Mousetrap (CEOI17_mousetrap)	C++17	25 / 100	1136 ms	76028 KiB

mousetrap

	#include<bits/stdc++.h>
	using namespace std;
	
	const int MAXN = 1000010;
	
	int n, t, m;
	int pai[MAXN], prof[MAXN];
	long long dp[MAXN];
	int marc[MAXN];
	long long ans;
	
	vector<int> ar[MAXN];
	
	void dfs(int cur);
	void getDP(int cur);
	
	int main(){
		scanf("%d %d %d", &n, &t, &m);
		for(int i = 1; i < n; i++){
			int a, b;
			scanf("%d %d", &a, &b);
			ar[a].push_back(b);
			ar[b].push_back(a);
		}
		dfs(t);
		stack<int> fila;
		int aux = m;
		while(aux != t){
			fila.push(aux);
			marc[aux] = 1;
			aux = pai[aux];
		}
		int sum = 0;
		while(!fila.empty()){
			getDP(fila.top());
			ans = max(ans, dp[fila.top()] + sum + prof[m] - prof[fila.top()]);
			sum += ar[fila.top()].size() - 2;
			fila.pop();
		}
		printf("%lld\n", ans);
	}
	
	void dfs(int cur){
		for(int i = 0; i < ar[cur].size(); i++){
			int viz = ar[cur][i];
			if(viz == pai[cur]) continue;
			prof[viz] = prof[cur] + 1;
			pai[viz] = cur;
			dfs(viz);
		}
	}
	
	void getDP(int cur){
		marc[cur] = 1;
		pair<long long, long long> aux = make_pair(0, 0);
		int tam = 0;
		for(int i = 0; i < ar[cur].size(); i++){
			int viz = ar[cur][i];
			if(viz == pai[cur]) continue;
			if(marc[viz]) continue;
			getDP(viz);
			if(dp[viz] > aux.first) aux.second = aux.first, aux.first = dp[viz];
			else aux.second = max(aux.second, dp[viz]);
			tam++;
		}
		dp[cur] = aux.second + 1 + tam - 1;
		if(tam == 0) dp[cur] = 0;
	}

Compilation message (stderr)

mousetrap.cpp: In function 'void dfs(int)':
mousetrap.cpp:44:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   44 |   for(int i = 0; i < ar[cur].size(); i++){
      |                  ~~^~~~~~~~~~~~~~~~
mousetrap.cpp: In function 'void getDP(int)':
mousetrap.cpp:57:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   57 |   for(int i = 0; i < ar[cur].size(); i++){
      |                  ~~^~~~~~~~~~~~~~~~
mousetrap.cpp: In function 'int main()':
mousetrap.cpp:18:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   18 |   scanf("%d %d %d", &n, &t, &m);
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
mousetrap.cpp:21:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   21 |    scanf("%d %d", &a, &b);
      |    ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 20
• Subtask 2: 25 / 25
• Subtask 3: 0 / 20
• Subtask 4: 0 / 35