#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
struct node {
node *nxt;
int first, second;
};
int n;
vector<node*> adj; // length, node
vector<bool> vst;
vector<int> comps;
vector<bool> cyc;
vector<pair<int, int>> nxt; // length, node
vector<ll> treeSz;
int cycRoot;
ll dfsCyc(int &cur, int &par) {
vst[cur] = true;
{
ll numECnt = 0;
node *e = adj[cur];
while (e != nullptr) {
if (e->second == par) {
numECnt++;
}
e = e->nxt;
}
if (numECnt == 2) {
pair<int, int> numE[2];
node *e = adj[cur];
while (e != nullptr) {
if (e->second == par) {
numE[--numECnt] = {e->first, e->second};
}
e = e->nxt;
}
vst[numE[0].second] = true;
cyc[cur] = cyc[numE[0].second] = true;
cycRoot = cur;
nxt[cur] = numE[0];
nxt[numE[0].second] = {numE[1].first, cur};
return -1;
}
}
node *e = adj[cur];
while (e != nullptr) {
if (e->second == par) { e = e->nxt; continue; }
if (vst[e->second] && !cyc[e->second]) {
cyc[cur] = true;
nxt[cur] = {e->first, e->second};
cycRoot = e->second;
return e->second;
}
else {
ll val = dfsCyc(e->second, cur);
if (val == -1) { e = e->nxt; continue; }
cyc[cur] = true;
nxt[cur] = {e->first, e->second};
return cur == val ? -1 : val;
}
e = e->nxt;
}
return -1;
}
ll mxLen = 0;
ll dfsTreeSz(int &cur, int &par) {
ll mx = 0;
ll nxtMx = 0;
node *e = adj[cur];
while (e != nullptr) {
if (e->second == par) { e = e->nxt; continue; }
if (cyc[e->second]) { e = e->nxt; continue; }
ll val = e->first + dfsTreeSz(e->second, cur);
if (val > mx) {
nxtMx = mx;
mx = val;
}
else if (val > nxtMx) {
nxtMx = val;
}
e = e->nxt;
}
mxLen = max(mxLen, nxtMx + mx);
return mx;
}
ll solveComp(int &root) {
mxLen = 0;
int minusOne = -1;
dfsCyc(root, minusOne);
int x = cycRoot;
vector<int> cycle;
do {
cycle.push_back(x);
x = nxt[x].second;
} while (x != cycRoot);
for (int i = 0; i < cycle.size(); i++) {
treeSz[cycle[i]] = dfsTreeSz(cycle[i], minusOne);
}
ll res = mxLen;
int mxId = cycle[0];
ll mxVal = treeSz[cycle[0]];
ll lenSum = 0;
int cur = cycle[0];
for (int i = 0; i < cycle.size(); i++) {
if (cur == cycle[i] || mxId == cycle[i]) {
cur = cycle[i];
lenSum = nxt[cur].first;
cur = nxt[cur].second;
mxId = cur;
mxVal = lenSum + treeSz[cur];
}
while (cur != cycle[i]) {
ll val = lenSum + treeSz[cur];
if (val >= mxVal) {
mxVal = val;
mxId = cur;
}
lenSum += nxt[cur].first;
cur = nxt[cur].second;
}
res = max(res, treeSz[cycle[i]] + mxVal);
lenSum -= nxt[cycle[i]].first;
mxVal -= nxt[cycle[i]].first;
}
return res;
}
void dfs1(int &cur) {
vst[cur] = true;
node *e = adj[cur];
while (e != nullptr) {
if (vst[e->second]) { e = e->nxt; continue; }
dfs1(e->second);
e = e->nxt;
}
}
int main() {
cin >> n;
adj = vector<node*>(n);
cyc = vector<bool>(n);
nxt = vector<pair<int, int>>(n);
treeSz = vector<ll>(n);
if (n >= 1000000) return 0;
for (int i = 0; i < n; i++) {
ll a, l;
cin >> a >> l;
node* nw = new node();
nw->first = l;
nw->second = a-1;
nw->nxt = adj[i];
adj[i] = nw;
nw = new node();
nw->first = l;
nw->second = i;
nw->nxt = adj[a-1];
adj[a-1] = nw;
}
vst = vector<bool>(n);
for (int i = 0; i < n; i++) {
if (vst[i]) continue;
dfs1(i);
comps.push_back(i);
}
vst = vector<bool>(n);
ll res = 0;
for (auto &e : comps) {
res += solveComp(e);
}
cout << res;
}
Compilation message
islands.cpp: In function 'll solveComp(int&)':
islands.cpp:101:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
101 | for (int i = 0; i < cycle.size(); i++) {
| ~~^~~~~~~~~~~~~~
islands.cpp:109:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
109 | for (int i = 0; i < cycle.size(); i++) {
| ~~^~~~~~~~~~~~~~
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1 ms |
344 KB |
Output is correct |
| 2 |
Correct |
0 ms |
348 KB |
Output is correct |
| 3 |
Correct |
0 ms |
348 KB |
Output is correct |
| 4 |
Correct |
0 ms |
348 KB |
Output is correct |
| 5 |
Correct |
0 ms |
348 KB |
Output is correct |
| 6 |
Correct |
0 ms |
348 KB |
Output is correct |
| 7 |
Correct |
0 ms |
348 KB |
Output is correct |
| 8 |
Correct |
0 ms |
348 KB |
Output is correct |
| 9 |
Correct |
0 ms |
344 KB |
Output is correct |
| 10 |
Correct |
0 ms |
348 KB |
Output is correct |
| 11 |
Correct |
1 ms |
348 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1 ms |
348 KB |
Output is correct |
| 2 |
Correct |
1 ms |
348 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1 ms |
604 KB |
Output is correct |
| 2 |
Correct |
4 ms |
860 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
8 ms |
1884 KB |
Output is correct |
| 2 |
Correct |
16 ms |
4700 KB |
Output is correct |
| 3 |
Correct |
12 ms |
2140 KB |
Output is correct |
| 4 |
Correct |
7 ms |
1116 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
24 ms |
6492 KB |
Output is correct |
| 2 |
Correct |
41 ms |
10580 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
87 ms |
19212 KB |
Output is correct |
| 2 |
Correct |
99 ms |
26808 KB |
Output is correct |
| 3 |
Correct |
129 ms |
34784 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
174 ms |
36164 KB |
Output is correct |
| 2 |
Correct |
558 ms |
60232 KB |
Output is correct |
| 3 |
Correct |
237 ms |
74464 KB |
Output is correct |
| 4 |
Correct |
337 ms |
87988 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
8 ms |
23896 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
9 ms |
23900 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
