Submission #309580

#	Time	Username	Problem	Language	Result	Execution time	Memory
309580		bigg	Mousetrap (CEOI17_mousetrap)	C++14	45 / 100	924 ms	60280 KiB

mousetrap

#include<bits/stdc++.h>
using namespace std;
const int MAXN = 1e6 + 10;
vector<int> grafo[MAXN];
int dp[MAXN];

pair<int, int > inserts(int x, pair<int, int> p){
	if(x >= p.first) swap(p.first, p.second), p.first = x;
	else if(x > p.second) p.second = x;
	return p;
}

void dfs(int x, int p){
	pair<int, int> par = make_pair(-1, -1);
	for(int i = 0; i < grafo[x].size(); i++){
		int viz = grafo[x][i];
		if(viz == p) continue;
		dfs(viz, x);
		par = inserts(dp[viz], par);
	}
	for(int i = 0 ; i < grafo[x].size(); i++){
		int viz = grafo[x][i];
		if(viz == p) swap(grafo[x][i], grafo[x].front());
	}
	if(grafo[x].size() == 1) dp[x] = 0;
	else{
		dp[x] = (grafo[x].size() == 2) ? 1 : par.second + grafo[x].size() - 1;
	}
	//printf("%d\n", dp[x]);
}
int n, t, m;
int main(){
	scanf("%d %d %d", &n, &t, &m);
	if(n == 1 || t == m){
		printf("0\n");
		return 0;
	}
	for(int i = 1; i < n; i++){
		int u, v;
		scanf("%d %d", &u, &v);
		grafo[u].push_back(v);
		grafo[v].push_back(u);
	}
	dfs(t, 0);
//	printf("oi\n");
	int ans = dp[m];
	m = grafo[m][0];
//	printf("%d\n",m );
	while(m != t){
		//printf("%d\n", m);
		ans += grafo[m].size() - 2;
		m = grafo[m][0];
	}
	printf("%d\n",ans);
}

Compilation message (stderr)

mousetrap.cpp: In function 'void dfs(int, int)':
mousetrap.cpp:15:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   15 |  for(int i = 0; i < grafo[x].size(); i++){
      |                 ~~^~~~~~~~~~~~~~~~~
mousetrap.cpp:21:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   21 |  for(int i = 0 ; i < grafo[x].size(); i++){
      |                  ~~^~~~~~~~~~~~~~~~~
mousetrap.cpp: In function 'int main()':
mousetrap.cpp:33:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   33 |  scanf("%d %d %d", &n, &t, &m);
      |  ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
mousetrap.cpp:40:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   40 |   scanf("%d %d", &u, &v);
      |   ~~~~~^~~~~~~~~~~~~~~~~

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