Submission #64462

#	Time	Username	Problem	Language	Result	Execution time	Memory
64462		Sherazin	Race (IOI11_race)	C++14	21 / 100	3030 ms	34652 KiB

race

//#include <race.h>
#include <bits/stdc++.h>

#define pii pair<int, int>
#define x first
#define y second

using namespace std;

const int N = 2e5 + 5;
const int M = 1e6 + 5;

int n, k, ans = -1;
int sub[N];
int dp[M], tim[M];
vector<pii> g[N];

int getsz(int u, int p) {
	sub[u] = 1;
	for(pii v : g[u]) if(v.x != p) sub[u] += getsz(v.x, u);
	return sub[u];	
}

void add(int u, int p, int cost, int len, int cnt) {
	if(cost > k) return;
	if(tim[k - cost] == cnt && (ans == -1 || len + dp[k - cost] < ans)) ans = len + dp[k - cost];
	if(cost == k && (ans == -1 || len < ans)) ans = len;
	for(pii v : g[u]) if(v.x != p) add(v.x, u, cost + v.y, len + 1, cnt);
}

void prep(int u, int p, int cost, int len, int cnt) {
	if(cost > k) return;
	if(tim[cost] != cnt || len < dp[cost]) tim[cost] = cnt, dp[cost] = len;
	for(pii v : g[u]) if(v.x != p) prep(v.x, u, cost + v.y, len + 1, cnt);
}

void dfs(int u, int p, bool keep, int cost) {
	int mx = 0, hv, hve;
	for(pii v : g[u]) if(v.x != p && mx < sub[v.x]) mx = sub[v.x], hv = v.x, hve = v.y;
	for(pii v : g[u]) if(v.x != p && v.x != hv) dfs(v.x, u, 0, v.y);
	if(mx) dfs(hv, u, 1, hve);
	for(pii v : g[u]) if(v.x != p && v.x != hv) {
		add(v.x, u, v.y, 1, u);
		prep(v.x, u, v.y, 1, u);
	}
	if(tim[k] == u && (ans == -1 || dp[k] < ans)) ans = dp[k]; 
	/*printf("%d: ", u);
	for(int i = 1; i <= k + 1; i++) {if(tim[i] == u) printf("%d ", dp[i]); else printf("X ");}
	printf("\n");*/
	if(keep) prep(u, p, cost, 1, p);
}

int best_path(int N, int K, int H[][2], int L[])
{
	n = N, k = K;
	for(int i = 0; i < N - 1; i++) {
		g[H[i][0]].emplace_back(H[i][1], L[i]);
		g[H[i][1]].emplace_back(H[i][0], L[i]);
	}
	fill(begin(tim), end(tim), -1);
	getsz(0, 0);
	dfs(0, 0, 1, 0);
 
	return ans;
}

/*int main() {
	scanf("%d%d", &n, &k);
	for(int i = 1, u, v, w; i <= n; i++) {
		scanf("%d%d%d", &u, &v, &w);
		g[u].emplace_back(v, w);
		g[v].emplace_back(u, w);
	}

	fill(begin(tim), end(tim), -1);
	getsz(0, 0);
	dfs(0, 0, 1, 0);	
	printf("%d", ans);

	return 0;
}*/

Compilation message (stderr)

race.cpp: In function 'void dfs(int, int, bool, int)':
race.cpp:40:32: warning: 'hv' may be used uninitialized in this function [-Wmaybe-uninitialized]
  for(pii v : g[u]) if(v.x != p && v.x != hv) dfs(v.x, u, 0, v.y);
                       ~~~~~~~~~^~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 12 / 12
• Subtask 3: 0 / 22
• Subtask 4: 0 / 57