//Never stop trying
#include "bits/stdc++.h"
using namespace std;
#define boost ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)
typedef long long ll;
typedef string str;
typedef long double ld;
typedef pair<int, int> pi;
#define fi first
#define se second
typedef vector<int> vi;
typedef vector<pi> vpi;
#define pb push_back
#define eb emplace_back
#define sz(x) (int)x.size()
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define endl "\n"
#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
const int MOD = 1e9 + 7; //998244353
const ll INF = 1e18;
const int MX = 1e6 + 10;
const int nx[4] = {0, 0, 1, -1}, ny[4] = {1, -1, 0, 0}; //right left down up
template<class T> bool ckmin(T& a, const T& b) { return a > b ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }
ll cdiv(ll a, ll b) { return a / b + ((a ^ b) > 0 && a % b); } // divide a by b rounded up
//constexpr int log2(int x) { return 31 - __builtin_clz(x); } // floor(log2(x))
mt19937 rng(chrono::system_clock::now().time_since_epoch().count());
//mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());
ll random(ll a, ll b){
return a + rng() % (b - a + 1);
}
#ifndef LOCAL
#define cerr if(false) cerr
#endif
#define dbg(x) cerr << #x << " : " << x << endl;
#define dbgs(x,y) cerr << #x << " : " << x << " / " << #y << " : " << y << endl;
#define dbgv(v) cerr << #v << " : " << "[ "; for(auto it : v) cerr << it << ' '; cerr << ']' << endl;
#define here() cerr << "here" << endl;
void IO() {
#ifdef LOCAL
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
}
/////////////////////////ONLY CLEAN CODES ALLOWED/////////////////////////
//--------------------------------------------
vi p(MX,-1);
int findSet(int u){
return p[u]==-1 ? u : p[u]=findSet(p[u]);
}
void joinSet(int u, int v){
u=findSet(u); v=findSet(v);
p[v]=u;
}
//-------------------------------------------------
int N;
vpi adj[MX];
vi vec,vis(MX,0);
void divide(int u){
if(vis[u]) return;
vis[u]=1;
vec.pb(u);
for(auto it: adj[u]){
int v=it.fi;
divide(v);
}
}
//Cycle building
vpi tree[MX];
//vpi par(MX);
vpi cy;
int U,V,W;
void find_cycle(int u, int pr){
/*for(auto it: tree[u]){
int v=it.fi,w=it.se;
if(v!=pr){
par[v]={u,w};
find_cycle(v,u);
}
}*/
if(sz(cy)) return;
if(u==V){
cy.eb(V,W);
return;
}
for(auto it: tree[u]){
int v=it.fi,w=it.se;
if(v!=pr){
find_cycle(v,u);
if(sz(cy)){
cy.eb(u,w);
break;
}
}
}
}
void build_cycle(){
for(int u: vec){
for(auto it: adj[u]){
int v=it.fi,w=it.se;
if(u<v){
if(findSet(u)!=findSet(v)){
joinSet(u,v);
tree[u].eb(v,w);
tree[v].eb(u,w);
}
else U=u,V=v,W=w;
}
}
}
//par[U]={V,W};
cy.clear();
find_cycle(U,U);
reverse(all(cy));
/*
int cur=V;
while(1){
cy.eb(cur,par[cur].se);
if(cur==U) break;
cur=par[cur].fi;
}*/
}
//new graph building
vpi temp[MX];
vi v1(MX,-1),v2(MX,-1);
void build_graph(){
int n=sz(cy);
FOR(i,0,n){
int u=cy[i].fi;
v1[u]=cy[(i-1+n)%n].fi,v2[u]=cy[(i+1)%n].fi;
}
for(int u: vec){
for(auto it: adj[u]){
int v=it.fi,w=it.se;
if(v==v1[u] || v==v2[u]) continue;
temp[u].eb(v,w);
}
}
for(int u: vec){
adj[u].assign(all(temp[u]));
}
}
//computing
vector<ll> dist(MX,-1);
vi viss;
void dfs(int u){
viss.pb(u);
for(auto it: adj[u]){
int v=it.fi,w=it.se;
if(dist[v]==-1){
dist[v]=dist[u]+w;
dfs(v);
}
}
}
int get_farthest(){
ll mx=-1,u;
for(int cur: viss) if(ckmax(mx,dist[cur])) u=cur;
return u;
}
ll compute_diam(int u){
dist[u]=0;
dfs(u);
u=get_farthest();
for(int node: viss) dist[node]=-1;
viss.clear();
dist[u]=0;
dfs(u);
int v=get_farthest();
ll ans=dist[v];
for(int node: viss) dist[node]=-1;
viss.clear();
return ans;
}
ll compute_max_len(int u, int p){
ll ans=0;
for(auto it: adj[u]){
int v=it.fi,w=it.se;
if(v!=p) ckmax(ans,compute_max_len(v,u)+w);
}
return ans;
}
ll compute(){
int n=sz(cy);
ll max_len[n],diam[n],S,s[n];
S=0;
FOR(i,0,sz(cy)){
S+=cy[i].se;
if(!i) s[i]=0;
else s[i]=s[i-1]+cy[i-1].se;
diam[i]=compute_diam(cy[i].fi);
max_len[i]=compute_max_len(cy[i].fi,cy[i].fi);
}
ll ans=0;
FOR(i,0,n) ckmax(ans,diam[i]);
ll mx_val1=-INF,mx_val2=-INF;
FOR(i,0,n){
if(i) ckmax(ans,max_len[i]+s[i]+mx_val1);
ckmax(mx_val1,max_len[i]-s[i]);
if(i) ckmax(ans,S+max_len[i]-s[i]+mx_val2);
ckmax(mx_val2,max_len[i]+s[i]);
}
return ans;
}
int main() {
boost; IO();
cin>>N;
FOR(i,1,N+1){
int j,w; cin>>j>>w;
adj[i].eb(j,w);
adj[j].eb(i,w);
}
ll ans=0;
FOR(i,1,N+1) if(!vis[i]){
vec.clear();
divide(i); //new component
build_cycle();
build_graph();
ans+=compute();
}
cout << ans << endl;
return 0;
}
//Change your approach
Compilation message
islands.cpp: In function 'int get_farthest()':
islands.cpp:186:9: warning: 'u' may be used uninitialized in this function [-Wmaybe-uninitialized]
186 | return u;
| ^
islands.cpp: In function 'll compute_diam(int)':
islands.cpp:199:15: warning: 'u' may be used uninitialized in this function [-Wmaybe-uninitialized]
199 | ll ans=dist[v];
| ^
islands.cpp:186:9: warning: 'u' may be used uninitialized in this function [-Wmaybe-uninitialized]
186 | return u;
| ^
islands.cpp:184:11: note: 'u' was declared here
184 | ll mx=-1,u;
| ^
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
51 ms |
94148 KB |
Output is correct |
| 2 |
Correct |
52 ms |
94188 KB |
Output is correct |
| 3 |
Correct |
51 ms |
94232 KB |
Output is correct |
| 4 |
Correct |
51 ms |
94208 KB |
Output is correct |
| 5 |
Correct |
51 ms |
94148 KB |
Output is correct |
| 6 |
Correct |
51 ms |
94148 KB |
Output is correct |
| 7 |
Correct |
52 ms |
94140 KB |
Output is correct |
| 8 |
Correct |
54 ms |
94204 KB |
Output is correct |
| 9 |
Correct |
51 ms |
94148 KB |
Output is correct |
| 10 |
Correct |
59 ms |
94276 KB |
Output is correct |
| 11 |
Correct |
52 ms |
94240 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
53 ms |
94396 KB |
Output is correct |
| 2 |
Correct |
53 ms |
94396 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
54 ms |
94356 KB |
Output is correct |
| 2 |
Correct |
64 ms |
94844 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
64 ms |
95912 KB |
Output is correct |
| 2 |
Correct |
87 ms |
99408 KB |
Output is correct |
| 3 |
Correct |
73 ms |
96708 KB |
Output is correct |
| 4 |
Correct |
61 ms |
95372 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
93 ms |
101444 KB |
Output is correct |
| 2 |
Correct |
107 ms |
105212 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
212 ms |
118416 KB |
Output is correct |
| 2 |
Correct |
181 ms |
118808 KB |
Output is correct |
| 3 |
Runtime error |
192 ms |
131072 KB |
Execution killed with signal 9 |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
250 ms |
131076 KB |
Execution killed with signal 9 |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
322 ms |
131076 KB |
Execution killed with signal 9 |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
351 ms |
131076 KB |
Execution killed with signal 9 |
| 2 |
Halted |
0 ms |
0 KB |
- |
