File size: 4,265 Bytes
1fd0050 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 | #include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int n, m;
if (!(cin >> n >> m)) return 0;
// scoring parameters, not used
for (int i = 0; i < 10; ++i) {
int x; cin >> x;
}
vector<vector<int>> out(n + 1), in(n + 1);
out.reserve(n + 1);
in.reserve(n + 1);
for (int i = 0; i < m; ++i) {
int u, v;
cin >> u >> v;
out[u].push_back(v);
in[v].push_back(u);
}
// Choose a good starting vertex: maximum total degree
int start = 1;
size_t bestDeg = 0;
for (int i = 1; i <= n; ++i) {
size_t d = out[i].size() + in[i].size();
if (d > bestDeg) {
bestDeg = d;
start = i;
}
}
// Data structures for path as a doubly linked list
vector<int> nxt(n + 1, -1), prv(n + 1, -1);
vector<char> inPath(n + 1, 0);
vector<int> outPtr(n + 1, 0), inPtr(n + 1, 0);
int head = start, tail = start;
inPath[start] = 1;
auto extendEnds = [&]() -> bool {
bool extended = false;
while (true) {
bool did = false;
// Extend at tail using out-edges
while (outPtr[tail] < (int)out[tail].size()) {
int v = out[tail][outPtr[tail]++];
if (!inPath[v]) {
// append v
nxt[tail] = v;
prv[v] = tail;
nxt[v] = -1;
inPath[v] = 1;
tail = v;
did = true;
extended = true;
break; // try extending further from new tail
}
}
if (did) continue;
// Extend at head using in-edges
while (inPtr[head] < (int)in[head].size()) {
int u = in[head][inPtr[head]++];
if (!inPath[u]) {
// prepend u
prv[head] = u;
nxt[u] = head;
prv[u] = -1;
inPath[u] = 1;
head = u;
did = true;
extended = true;
break; // try extending further from new head
}
}
if (!did) break;
}
return extended;
};
// Initial greedy extension
extendEnds();
// Insertion heuristic
vector<int> mark(n + 1, 0);
int stamp = 1;
auto insertionPass = [&]() -> bool {
bool insertedAny = false;
for (int u = 1; u <= n; ++u) {
if (inPath[u]) continue;
// mark out-neighbors that are in the current path
if (++stamp == INT_MAX - 1) {
// reset marks to avoid overflow
fill(mark.begin(), mark.end(), 0);
stamp = 1;
}
for (int v : out[u]) {
if (inPath[v]) mark[v] = stamp;
}
bool inserted = false;
for (int x : in[u]) {
if (!inPath[x]) continue;
int y = nxt[x];
if (y != -1 && mark[y] == stamp) {
// insert u between x and y
nxt[x] = u;
prv[u] = x;
nxt[u] = y;
prv[y] = u;
inPath[u] = 1;
inserted = true;
insertedAny = true;
break;
}
}
// no push-front/back here; extendEnds() will handle those
}
return insertedAny;
};
// Iterate insertion + extension until no progress
while (true) {
bool changed = false;
if (extendEnds()) changed = true;
if (insertionPass()) changed = true;
if (extendEnds()) changed = true;
if (!changed) break;
}
// Extract path
vector<int> path;
path.reserve(n);
int cur = head;
while (cur != -1) {
path.push_back(cur);
cur = nxt[cur];
}
cout << (int)path.size() << "\n";
for (size_t i = 0; i < path.size(); ++i) {
if (i) cout << ' ';
cout << path[i];
}
cout << "\n";
return 0;
} |