#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define mp make_pair
#define pb push_back
typedef pair<int, int> ii;
const int len = 1e6+5, inf = 1e9;
vector<int> adj[len], cost[len], order;
int block[len], dp[2][len];
int fix_order(int u, int p, int en){
if (u == en){
block[u] = 1;
return 1;
}
for (auto v: adj[u]){
if (v == p) continue;
if (fix_order(v, u, en)){
order.pb(u);
block[u] = 1;
return 1;
}
}
return 0;
}
int run_dfs(int u, int p){
int mx1 = 0, mx2 = 0, kids = 0;
for (auto v: adj[u]){
if (v == p) continue;
kids++;
int cur = run_dfs(v, u);
if (cur > mx1)
mx2 = mx1, mx1 = cur;
else if (cur > mx2)
mx2 = cur;
}
return mx2+kids;
}
int main(){
freopen("trap.01.01.in", "r", stdin);
int n, en, st;
scanf("%d %d %d", &n, &en, &st);
for (int i = 0; i < n-1; i++){
int a, b;
scanf("%d %d", &a, &b);
adj[a].pb(b);
adj[b].pb(a);
}
fix_order(st, st, en);
reverse(order.begin(), order.end());
for (int i = (int)order.size()-1, cnt = 0; i >= 0; i--){
int u = order[i];
//printf("i = %d, u = %d\n", i, u);
for (auto v: adj[u]){
if (block[v]) continue;
cost[i].pb(run_dfs(v, u)+1);
//printf("%d -> %d, cost = %d\n", u, v, cost[i].back());
}
sort(cost[i].begin(), cost[i].end());
reverse(cost[i].begin(), cost[i].end());
for (int j = (int)cost[i].size()-1; j >= 0; j--)
cost[i][j] += cnt++;
cost[i].pb(0);
/*printf("i = %d\n", i);
for (int j = 0; j < cost[i].size(); j++)
printf("%d ", cost[i][j]);
printf("\n");*/
}
for (int i = (int)order.size()-1; i >= 0; i--){
for (int rem = 1; rem <= i+1; rem++){
//printf("computing dp: i = %d, rem = %d\n", i, rem);
dp[i&1][rem] = inf;
//if (rem >= cost[i].size())
// dp[i&1][rem] = cost[i].size() + dp[(i+1)&1][rem-cost[i].size()+1];
int opt = -1;
for (int j = 0; j < cost[i].size() && j <= rem; j++){
if (cost[i][j] >= dp[(i+1)&1][rem-j+1])
opt = j;
//dp[i&1][rem] = min(dp[i&1][rem], j+max(cost[i][j], dp[(i+1)&1][rem-j+1]));
}
//printf("opt = %d\n", opt);
if (opt != -1)
dp[i&1][rem] = opt + cost[i][opt];
else
dp[i&1][rem] = dp[(i+1)&1][rem+1];
}
//printf("i = %d\n", i);
for (int rem = 2; rem <= i+1; rem++)
assert(dp[i&1][rem] <= dp[i&1][rem-1]);
//printf("rem = %d, dp = %d\n", rem, dp[i&1][rem]);
}
printf("%d\n", dp[0][1]);
return 0;
}
Compilation message
mousetrap.cpp: In function 'int main()':
mousetrap.cpp:100:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
100 | for (int j = 0; j < cost[i].size() && j <= rem; j++){
| ~~^~~~~~~~~~~~~~~~
mousetrap.cpp:51:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
51 | freopen("trap.01.01.in", "r", stdin);
| ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mousetrap.cpp:54:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
54 | scanf("%d %d %d", &n, &en, &st);
| ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
mousetrap.cpp:57:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
57 | scanf("%d %d", &a, &b);
| ~~~~~^~~~~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
32 ms |
47224 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
55 ms |
47224 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
32 ms |
47224 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
32 ms |
47224 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
