//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> using V = vector<T>;
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/////////////////////////
//--------------------------------------------
int p[MX];
int findSet(int u){
return p[u]==u ? 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);
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);
}
}
}
vpi cy;
void build_cycle(){
int U,V,W;
for(int u: vec) p[u]=u;
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};
find_cycle(U,U);
cy.clear();
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
ll max_len[MX],diam[MX],S,s[MX];
V<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(){
S=0;
int n=sz(cy);
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=0,mx_val2=0;
FOR(i,0,n){
ckmax(ans,max_len[i]+s[i])+mx_val1;
ckmax(mx_val1,max_len[i]-s[i]);
ckmax(ans,S+max_len[i]-s[i])+mx_val2;
ckmax(mx_val1,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 'll compute()':
islands.cpp:218:29: warning: value computed is not used [-Wunused-value]
218 | ckmax(ans,max_len[i]+s[i])+mx_val1;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
islands.cpp:221:31: warning: value computed is not used [-Wunused-value]
221 | ckmax(ans,S+max_len[i]-s[i])+mx_val2;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
islands.cpp: In function 'int get_farthest()':
islands.cpp:171:9: warning: 'u' may be used uninitialized in this function [-Wmaybe-uninitialized]
171 | return u;
| ^
islands.cpp: In function 'll compute_diam(int)':
islands.cpp:184:15: warning: 'u' may be used uninitialized in this function [-Wmaybe-uninitialized]
184 | ll ans=dist[v];
| ^
islands.cpp:171:9: warning: 'u' may be used uninitialized in this function [-Wmaybe-uninitialized]
171 | return u;
| ^
islands.cpp:169:11: note: 'u' was declared here
169 | ll mx=-1,u;
| ^
islands.cpp: In function 'void build_cycle()':
islands.cpp:118:6: warning: 'V' may be used uninitialized in this function [-Wmaybe-uninitialized]
118 | int cur=V;
| ^~~
islands.cpp:114:7: warning: 'U' may be used uninitialized in this function [-Wmaybe-uninitialized]
114 | par[U]={V,W};
| ^
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
57 ms |
98224 KB |
Output isn't correct |
| 2 |
Incorrect |
56 ms |
98136 KB |
Output isn't correct |
| 3 |
Incorrect |
56 ms |
98204 KB |
Output isn't correct |
| 4 |
Incorrect |
63 ms |
98208 KB |
Output isn't correct |
| 5 |
Incorrect |
56 ms |
98124 KB |
Output isn't correct |
| 6 |
Incorrect |
57 ms |
98200 KB |
Output isn't correct |
| 7 |
Incorrect |
60 ms |
98212 KB |
Output isn't correct |
| 8 |
Incorrect |
58 ms |
98152 KB |
Output isn't correct |
| 9 |
Incorrect |
56 ms |
98120 KB |
Output isn't correct |
| 10 |
Correct |
59 ms |
98152 KB |
Output is correct |
| 11 |
Incorrect |
55 ms |
98116 KB |
Output isn't correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
57 ms |
98264 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
59 ms |
98336 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
69 ms |
100032 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
100 ms |
105912 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Incorrect |
216 ms |
123560 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
243 ms |
131076 KB |
Execution killed with signal 9 |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
292 ms |
131076 KB |
Execution killed with signal 9 |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Runtime error |
366 ms |
131076 KB |
Execution killed with signal 9 |
| 2 |
Halted |
0 ms |
0 KB |
- |
