#include <bits/stdc++.h>
using namespace std;
using pi = pair<int, int>;
pi operator +(pi a, int b) {
return {a.first + b,a.second + b};
}
int travelTime(int n, int m, int cost, int A[], int B[], int T[]) {
int ans = 0, t = 0;
vector<int> seen(n), cn;
vector<pi> dpu(n, {-0x3F3F3F3F,-0x3F3F3F3F}), dpb(n, {-0x3F3F3F3F,-0x3F3F3F3F});
vector<vector<pi>> pref(n), suf(n);
vector<pair<pi, int>> cur;
vector<vector<pair<int, int>>> G(n);
for (int i = 0; i < m; ++i) {
G[A[i]].emplace_back(B[i], T[i]);
G[B[i]].emplace_back(A[i], T[i]);
}
auto combine = [&](pi a, pi b) {
pi ans;
if (b > a)
swap(a, b);
ans.first = a.first;
ans.second = max(a.second, b.first);
return ans;
};
function<void(int, int)> dfs = [&](int node, int last) {
cn.emplace_back(node);
seen[node] = t;
pref[node].emplace_back(-0x3F3F3F3F, -0x3F3F3F3F), suf[node].emplace_back(-0x3F3F3F3F, -0x3F3F3F3F);
int leaf = 1;
for (auto x : G[node])
if (x.first != last) {
leaf = 0;
dfs(x.first, node);
dpb[node] = combine(dpb[node], dpb[x.first] + x.second);
pref[node].emplace_back(dpb[x.first] + x.second);
suf[node].emplace_back(dpb[x.first] + x.second);
}
if (leaf)
dpb[node].first = 0;
pref[node].emplace_back(-0x3F3F3F3F, -0x3F3F3F3F), suf[node].emplace_back(-0x3F3F3F3F, -0x3F3F3F3F);
int s = pref[node].size();
for (int i = 1; i <= s - 1; ++i)
pref[node][i] = combine(pref[node][i], pref[node][i - 1]);
for (int i = s - 2; i; --i)
suf[node][i] = combine(suf[node][i], suf[node][i + 1]);
};
function<void(int, int)> dfs2 = [&](int node, int last) {
int ct = 1;
for (auto x : G[node])
if (x.first != last) {
dpu[x.first] = combine(combine(pref[node][ct - 1], suf[node][ct + 1]), dpu[node]) + x.second;
//cout << x.first << ' ' << combine(pref[node][ct - 1], suf[node][ct + 1]).first << ' ' << dpu[x.first].first << '\n';
dfs2(x.first, node);
++ct;
}
};
for (int i = 0; i < n; ++i)
if (!seen[i]) {
++t;
cn.clear();
dfs(i, -1);
dpu[i] = {0,0};
dfs2(i, -1);
pair<pi, int> ans = {{0x3F3F3F3F,0x3F3F3F3F}, 0};
//cout << "ROOT : " << i << '\n';
for (auto x : cn)
//printf("%d : U %d D %d\n", x, dpu[x].first, dpb[x].first),
ans = min(ans, {combine(dpu[x],dpb[x]),x});
cur.emplace_back(ans);
//cout << ans.first.first << ' ' << ans.first.second << ' ' << ans.second << '\n';
}
pair<pi, int> node = cur.back();
cur.pop_back();
for (auto [c, n] : cur) {
//cout << "ADD " << n << ' ' << node.second << '\n';
G[n].emplace_back(node.second, cost);
G[node.second].emplace_back(n, cost);
if (c < node.first)
node.first = combine(node.first, c + cost);
else
node.first = combine(node.first + cost, c), node.second = n;
}
//cout << node.first.first + node.first.second << '\n';
return node.first.first + node.first.second;
}
Compilation message
dreaming.cpp: In function 'int travelTime(int, int, int, int*, int*, int*)':
dreaming.cpp:11:6: warning: unused variable 'ans' [-Wunused-variable]
11 | int ans = 0, t = 0;
| ^~~
/usr/bin/ld: /tmp/ccMEMvFK.o: in function `main':
grader.c:(.text.startup+0xd1): undefined reference to `travelTime'
collect2: error: ld returned 1 exit status
