#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define vll vector<ll>
#define PB push_back
#define FOR(i, a, b) for (int i = int(a); i < int(b); i++)
#define REP(i, n) FOR(i, 0, n)
#define all(x) (x).begin(), (x).end()
const ll INF = (1 << 58);
const int MAXN = 1e6 + 7;
bool bio[MAXN];
int to[MAXN], w[MAXN];
vi g[MAXN];
ll ans, ret;
vll dp, s;
int ciklus(int u){
if(bio[u]) return u;
bio[u] = 1;
int v = ciklus(to[u]);
if(v){
dp.PB(u);
s.PB(w[u]);
if(u == v) return 0;
return v;
}
bio[u] = 0;
return 0;
}
ll dfs(int u){
ll mx = 0;
bio[u] = 1;
for(int &x : g[u]){
if(bio[x]) continue;
ll ch = w[x] + dfs(x);
ret = max(ret, (ll)ch + (ll)mx);
mx = max(mx, ch);
}
return mx;
}
void resi(int u){
dp.clear(), s.clear();
ciklus(u);
int sz = s.size();
reverse(all(dp));
reverse(all(s));
for(ll &x : dp) x = (ll)dfs(x);
for(int i = sz - 1; i; i--) swap(s[i], s[i - 1]);
FOR(i, 1, sz) s[i] += s[i - 1];
ll m1 = -INF, m2 = -INF;
REP(i, sz){
ret = max(ret, (ll)dp[i] + (ll)s[i] + (ll)m1);
ret = max(ret, (ll)s[sz - 1] + (ll)m2 + (ll)dp[i] - (ll)s[i]);
m1 = max(m1, (ll)dp[i] - (ll)s[i]);
m2 = max(m2, (ll)dp[i] + (ll)s[i]);
}
}
void solve(){
int n;
cin >> n;
FOR(i, 1, n + 1) cin >> to[i] >> w[i], g[to[i]].PB(i);
FOR(i, 1, n + 1) if(!bio[i]) ret = 0, resi(i), ans += ret;
cout << ans << "\n";
}
int main(){
//ios_base::sync_with_stdio(false);
//cin.tie(NULL);
//cout.tie(NULL);
int t=1;
//cin >> t;
while(t--)solve();
return 0;
}
Compilation message
islands.cpp:12:19: warning: left shift count >= width of type [-Wshift-count-overflow]
12 | const ll INF = (1 << 58);
| ~~^~~~~
islands.cpp:17:1: error: 'vi' does not name a type
17 | vi g[MAXN];
| ^~
islands.cpp: In function 'll dfs(int)':
islands.cpp:38:15: error: 'g' was not declared in this scope
38 | for(int &x : g[u]){
| ^
islands.cpp: In function 'void solve()':
islands.cpp:68:41: error: 'g' was not declared in this scope
68 | FOR(i, 1, n + 1) cin >> to[i] >> w[i], g[to[i]].PB(i);
| ^
