#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
struct SGT {
vector<ll> tree;
int sz;
SGT(int n) {
sz = 1;
while (sz < n)sz *= 2;
tree.resize(sz * 2);
}
ll query(int le, int ri) {
le += sz;
ri += sz;
ll ret = 0;
while (le <= ri) {
if (le & 1)ret = max(ret, tree[le++]);
if (!(ri & 1))ret = max(ret, tree[ri--]);
le /= 2;
ri /= 2;
}
return ret;
}
};
int n;
vector<tuple<int,int,int> > adj[1000005];
int trip[1000005];
bool chk[1000005], chk2[1000005];
vector<int> cycle,len;
vector<ll> d;
ll dd[1000005];
int r[1000005];
int vn;
void dfs(int now, int pw,int pi) {
r[now] = trip[now] = ++vn;
for (auto &e : adj[now]) {
if (get<2>(e)==pi)continue;
if (!trip[get<0>(e)]) {
dfs(get<0>(e), get<1>(e), get<2>(e));
r[now] = min(r[now], r[get<0>(e)]);
}
else if(!chk[get<0>(e)]){
r[now] = min(r[now], trip[get<0>(e)]);
cycle.push_back(get<0>(e));
chk[get<0>(e)] = true;
len.push_back(get<1>(e));
}
}
if (r[now] < trip[now]) {
chk[now] = true;
cycle.push_back(now);
len.push_back(pw);
}
}
ll val;
void dfs2(int now) {
chk[now] = true;
for (auto &e : adj[now]) {
if (chk[get<0>(e)])continue;
dfs2(get<0>(e));
val = max(val, dd[now] + dd[get<0>(e)] + get<1>(e));
dd[now] = max(dd[now], dd[get<0>(e)] + get<1>(e));
}
}
ll calc(vector<ll> d, vector<int> len, int m) {
vector<ll> ds(m);
for (int i = 1; i < m; i++)
ds[i] = ds[i - 1] + len[i - 1];
SGT sgt(m * 2);
ll sum = len[0];
for (int i = 1; i < m * 2; i++) {
sgt.tree[i + sgt.sz] = sum + d[i%m];
sum += len[i%m];
}
for (int i = sgt.sz - 1; i; i--)
sgt.tree[i] = max(sgt.tree[i * 2], sgt.tree[i * 2 + 1]);
ll ret = 0;
for (int i = 0; i < m; i++) {
ll temp = d[i] + sgt.query(i + 1, i + m - 1) - ds[i];
ret = max(ret, temp);
}
return ret;
}
int main() {
scanf("%d", &n);
for (int i = 1; i <= n; i++) {
int a, b;
scanf("%d%d", &a, &b);
adj[i].emplace_back(a, b, i);
adj[a].emplace_back(i, b, i);
}
ll ans = 0;
for (int i = 1; i <= n; i++) {
if (!trip[i]) {
cycle.clear();
len.clear();
d.clear();
dfs(i, 0, 0, 0);
int m = cycle.size();
d.resize(m);
val = 0;
for (int i = 0; i < cycle.size(); i++) {
dfs2(cycle[i]);
d[i] = dd[cycle[i]];
}
val = max(val,calc(d, len, m));
reverse(len.begin(), len.end() - 1);
reverse(d.begin(), d.end());
val = max(val, calc(d, len, m));
ans += val;
}
}
printf("%lld\n", ans);
return 0;
}
Compilation message
islands.cpp: In function 'int main()':
islands.cpp:98:18: error: too many arguments to function 'void dfs(int, int, int)'
dfs(i, 0, 0, 0);
^
islands.cpp:34:6: note: declared here
void dfs(int now, int pw,int pi) {
^~~
islands.cpp:102:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (int i = 0; i < cycle.size(); i++) {
~~^~~~~~~~~~~~~~
islands.cpp:85:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d", &n);
~~~~~^~~~~~~~~~
islands.cpp:88:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
scanf("%d%d", &a, &b);
~~~~~^~~~~~~~~~~~~~~~
