#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
typedef tree<int, null_type, less<int>, rb_tree_tag,tree_order_statistics_node_update> ordered_set;
#define scan(x) do{while((x=getchar())<'0'); for(x-='0'; '0'<=(_=getchar()); x=(x<<3)+(x<<1)+_-'0');}while(0)
char _;
#define complete_unique(a) a.erase(unique(a.begin(),a.end()),a.end())
#define all(a) a.begin(),a.end()
#define println printf("\n");
#define readln(x) getline(cin,x);
#define pb push_back
#define endl "\n"
#define INT_INF 0x3f3f3f3f
#define LL_INF 0x3f3f3f3f3f3f3f3f
#define MOD 1000000007
#define MOD2 1190492669
#define SEED 131
#define mp make_pair
#define fastio cin.tie(0); cin.sync_with_stdio(0);
#define MAXN 1000005
typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;
typedef unordered_map<int,int> umii;
typedef pair<int,int> pii;
typedef pair<double,double> pdd;
typedef pair<ll,ll> pll;
typedef pair<int,pii> triple;
typedef int8_t byte;
mt19937 g1(time(0));
int randint(int a, int b){return uniform_int_distribution<int>(a, b)(g1);}
ll randlong(ll a,ll b){return uniform_int_distribution<long long>(a, b)(g1);}
ll gcd(ll a, ll b){return b == 0 ? a : gcd(b, a % b);}
ll lcm(ll a, ll b){return a*b/gcd(a,b);}
ll fpow(ll b, ll exp, ll mod){if(exp == 0) return 1;ll t = fpow(b,exp/2,mod);if(exp&1) return t*t%mod*b%mod;return t*t%mod;}
ll divmod(ll i, ll j, ll mod){i%=mod,j%=mod;return i*fpow(j,mod-2,mod)%mod;}
int num_nodes,T,M,dp[MAXN],par[MAXN],depth[MAXN],sum[MAXN];
bool done[MAXN],marked[MAXN];
vector<int> connections[MAXN];
inline bool cmp(int a, int b){
return depth[a]>depth[b];
}
int dfs(int node, int prev){
for(int check:connections[node]){
if(check == prev) continue;
par[check] = node;
depth[check] = depth[node]+1;
dfs(check,node);
}
}
int solve(int node, int prev){
int bst = -1, bst2 = -1, cnt = 0;
for(int check:connections[node]){
if(check == prev) continue;
cnt++;
}
sum[node] = sum[prev]+cnt;
for(int check:connections[node]){
if(check == prev) continue;
int n = solve(check,node);
if(n >= bst) bst2 = bst, bst = n;
else if(n > bst2) bst2 = n;
}
if(cnt == 0) return dp[node] = 0;
if(bst2 == -1) return dp[node] = 1;
return dp[node] = bst2+cnt;
}
bool works(int mid){
memset(done,false,sizeof done);
deque<int> v;
int current = M, cnt = 0, og = 0;
while(current){
int mm = 0;
for(int check:connections[current]){
if(check == par[current] || marked[check]) continue;
int cost = cnt+sum[current]+dp[check]-depth[current];
if(cost > mid){
v.pb(check);
mm++;
}else done[check] = true;
}
cnt+=mm, og+=mm;
current = par[current];
}
sort(all(v),cmp);
current = M;
while(current){
if(v.size()){
int n = v.front(); v.pop_front();
done[n] = true;
}
for(int check:connections[current]){
if(check == par[current] || done[check] || marked[check]) continue;
return false;
}
current = par[current];
}
if(og <= mid) return true;
return false;
}
int main(){
scanf("%d %d %d",&num_nodes,&T,&M);
for(int i=1; i<num_nodes; i++){
int a,b; scanf(" %d %d",&a,&b);
connections[a].pb(b);
connections[b].pb(a);
}
dfs(T,-1);
solve(T,-1);
int curr = M;
while(curr){
marked[curr] = true;
curr = par[curr];
}
// cout<<works(0)<<endl;
int low = 0, high = 100000000, ans = high;
while(low <= high){
int mid = (low+high)/2;
if(works(mid)){
ans = mid;
high = mid-1;
}else low = mid+1;
}
printf("%d\n",ans);
}
/*
3 1 3
1 2
2 3
ans=0
*/
Compilation message
mousetrap.cpp: In function 'int dfs(int, int)':
mousetrap.cpp:62:1: warning: no return statement in function returning non-void [-Wreturn-type]
}
^
mousetrap.cpp: In function 'int main()':
mousetrap.cpp:117:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d %d %d",&num_nodes,&T,&M);
~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
mousetrap.cpp:119:17: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
int a,b; scanf(" %d %d",&a,&b);
~~~~~^~~~~~~~~~~~~~~~
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
26 ms |
24824 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
457 ms |
71884 KB |
Output is correct |
| 2 |
Correct |
411 ms |
67068 KB |
Output is correct |
| 3 |
Correct |
1124 ms |
72972 KB |
Output is correct |
| 4 |
Correct |
529 ms |
48956 KB |
Output is correct |
| 5 |
Correct |
1116 ms |
73108 KB |
Output is correct |
| 6 |
Correct |
1191 ms |
72876 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
26 ms |
24824 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
26 ms |
24824 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
