#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
const int N = 1000100;
int n;
ll ans = 0;
int len[N];
vector <pair<int, int> > g[N];
bool used[N], block[N];
int used2[N], pr[N], cEnd, cStrt, pr2[N];
int cId;
int fnd_cycle(int v, int p){
used2[v] = 1;
for (int i = 0; i < g[v].size(); i++){
int to = g[v][i].first, id = g[v][i].second;
if (id == p)
continue;
if (used2[to] == 0){
pr[to] = v;
pr2[to] = id;
if (fnd_cycle(to, id)){
return 1;
}
} else
if (used2[to] == 1){
cEnd = v;
cId = id;
cStrt = to;
return 1;
}
}
used2[v] = 2;
return 0;
}
ll dfs(int v, int p){
used[v] = 1;
ll curmx = 0;
for (int i = 0; i < g[v].size(); i++){
int to = g[v][i].first;
if (to == p)
continue;
curmx = max(curmx, dfs(to, v)+len[g[v][i].second]);
}
return curmx;
}
ll mx, mxver;
void dfs2(int v, int p, ll curlen){
if (curlen > mx){
mx = curlen;
mxver = v;
}
for (int i = 0; i < g[v].size(); i++){
int to = g[v][i].first;
if (!block[g[v][i].second] && to != p)
dfs2(to, v, curlen+len[g[v][i].second]);
}
}
ll fnd_diam(int v){
mx = -1, mxver = 0;
dfs2(v, 0, 0);
mx = -1;
dfs2(mxver, 0, 0);
return mx;
}
int main(){
ios_base::sync_with_stdio(0);cin.tie(0);
cin >> n;
for (int i = 1; i <= n; i++){
int to;
cin >> to >> len[i];
g[i].push_back({to, i});
g[to].push_back({i, i});
}
for (int i = 1; i <= n; i++){
if (used[i])
continue;
fnd_cycle(i, 0);
vector <int> cycle;
vector <ll> lens;
cycle.push_back(cStrt);
lens.push_back(0);
lens.push_back(len[cId]);
block[cId] = 1;
for (int v = cEnd; v != cStrt; v = pr[v]){
cId = pr2[v];
cycle.push_back(v);
lens.push_back(len[cId]);
block[cId] = 1;
}
for (int j = 1; j < lens.size(); j++){
lens[j] += lens[j-1];
}
ll curans = 0;
ll mx1 = -1e18, mx2 = -1e18;
for (int j = 0; j < cycle.size(); j++){
int v = cycle[j];
used[v] = 1;
ll curmx = 0;
for (int j = 0; j < g[v].size(); j++){
int to = g[v][j].first;
if (block[g[v][j].second])
continue;
curmx = max(curmx, dfs(to, v)+len[g[v][j].second]);
}
curans = max(curans, curmx);
curans = max(curans, fnd_diam(v));
if (j == 0){
mx1 = max(mx1, curmx);
mx2 = max(mx2, curmx);
} else {
curans = max(curans, curmx+lens[j] + mx1 );
curans = max(curans, curmx+lens.back()-lens[j] + mx2 );
mx1 = max(mx1, curmx-lens[j]);
mx2 = max(mx2, curmx+lens[j]);
}
}
ans += curans;
}
cout << ans;
}
Compilation message
islands.cpp: In function 'int fnd_cycle(int, int)':
islands.cpp:25:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (int i = 0; i < g[v].size(); i++){
~~^~~~~~~~~~~~~
islands.cpp: In function 'll dfs(int, int)':
islands.cpp:52:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (int i = 0; i < g[v].size(); i++){
~~^~~~~~~~~~~~~
islands.cpp: In function 'void dfs2(int, int, ll)':
islands.cpp:68:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (int i = 0; i < g[v].size(); i++){
~~^~~~~~~~~~~~~
islands.cpp: In function 'int main()':
islands.cpp:111:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (int j = 1; j < lens.size(); j++){
~~^~~~~~~~~~~~~
islands.cpp:119:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (int j = 0; j < cycle.size(); j++){
~~^~~~~~~~~~~~~~
islands.cpp:124:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
for (int j = 0; j < g[v].size(); j++){
~~^~~~~~~~~~~~~
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
21 ms |
23808 KB |
Output is correct |
| 2 |
Correct |
20 ms |
23928 KB |
Output is correct |
| 3 |
Correct |
21 ms |
23936 KB |
Output is correct |
| 4 |
Correct |
20 ms |
23808 KB |
Output is correct |
| 5 |
Correct |
21 ms |
23808 KB |
Output is correct |
| 6 |
Correct |
21 ms |
23936 KB |
Output is correct |
| 7 |
Correct |
22 ms |
23908 KB |
Output is correct |
| 8 |
Correct |
21 ms |
23936 KB |
Output is correct |
| 9 |
Correct |
23 ms |
23936 KB |
Output is correct |
| 10 |
Correct |
25 ms |
23900 KB |
Output is correct |
| 11 |
Correct |
21 ms |
23936 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
21 ms |
23928 KB |
Output is correct |
| 2 |
Correct |
22 ms |
23936 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
22 ms |
23932 KB |
Output is correct |
| 2 |
Correct |
24 ms |
24292 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
29 ms |
25060 KB |
Output is correct |
| 2 |
Correct |
42 ms |
27256 KB |
Output is correct |
| 3 |
Correct |
36 ms |
25436 KB |
Output is correct |
| 4 |
Correct |
28 ms |
24568 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
47 ms |
28664 KB |
Output is correct |
| 2 |
Correct |
60 ms |
31256 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
128 ms |
36972 KB |
Output is correct |
| 2 |
Correct |
119 ms |
40268 KB |
Output is correct |
| 3 |
Correct |
137 ms |
48368 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
166 ms |
47044 KB |
Output is correct |
| 2 |
Correct |
222 ms |
65204 KB |
Output is correct |
| 3 |
Correct |
236 ms |
69656 KB |
Output is correct |
| 4 |
Correct |
293 ms |
84576 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
339 ms |
76496 KB |
Output is correct |
| 2 |
Correct |
907 ms |
105008 KB |
Output is correct |
| 3 |
Correct |
323 ms |
69540 KB |
Output is correct |
| 4 |
Correct |
443 ms |
97312 KB |
Output is correct |
| 5 |
Correct |
405 ms |
98052 KB |
Output is correct |
| 6 |
Correct |
1710 ms |
77276 KB |
Output is correct |
| 7 |
Correct |
446 ms |
131072 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Runtime error |
413 ms |
131072 KB |
Execution killed with signal 9 (could be triggered by violating memory limits) |
| 2 |
Halted |
0 ms |
0 KB |
- |
