File size: 5,335 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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 | #include <bits/stdc++.h>
using namespace std;
struct FastScanner {
static const int BUFSIZE = 1 << 20;
int idx, size;
char buf[BUFSIZE];
FastScanner(): idx(0), size(0) {}
inline char getcharFast() {
if (idx >= size) {
size = (int)fread(buf, 1, BUFSIZE, stdin);
idx = 0;
if (size == 0) return 0;
}
return buf[idx++];
}
template <typename T>
bool readInt(T &out) {
char c; T sign = 1; T val = 0;
c = getcharFast();
if (!c) return false;
while (c!='-' && (c<'0' || c>'9')) {
c = getcharFast();
if (!c) return false;
}
if (c=='-') { sign = -1; c = getcharFast(); }
for (; c>='0' && c<='9'; c=getcharFast())
val = val*10 + (c - '0');
out = val * sign;
return true;
}
};
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
FastScanner fs;
int n, m;
if (!fs.readInt(n)) return 0;
fs.readInt(m);
// read scoring params, but unused for algorithm
for (int i = 0; i < 10; ++i) {
int tmp; fs.readInt(tmp);
}
vector<vector<int>> out(n+1), in(n+1);
out.reserve(n+1); in.reserve(n+1);
out.shrink_to_fit(); in.shrink_to_fit();
vector<int> degOut(n+1,0), degIn(n+1,0);
for (int i = 0; i < m; ++i) {
int u, v; fs.readInt(u); fs.readInt(v);
out[u].push_back(v);
in[v].push_back(u);
degOut[u]++; degIn[v]++;
}
// Shuffle adjacency for randomness
std::mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
for (int i = 1; i <= n; ++i) {
auto &vo = out[i];
if (!vo.empty()) shuffle(vo.begin(), vo.end(), rng);
auto &vi = in[i];
if (!vi.empty()) shuffle(vi.begin(), vi.end(), rng);
}
// Candidate seeds: high degree nodes and random picks
vector<int> nodes(n);
iota(nodes.begin(), nodes.end(), 1);
// compute combined degree
vector<pair<long long,int>> degScore;
degScore.reserve(n);
for (int i = 1; i <= n; ++i) {
degScore.emplace_back((long long)degOut[i] + (long long)degIn[i], i);
}
sort(degScore.begin(), degScore.end(), greater<pair<long long,int>>());
vector<int> seeds;
int topK = min(n, 10);
for (int i = 0; i < topK; ++i) seeds.push_back(degScore[i].second);
// also include max outdeg and max indeg
int maxOut = max_element(degOut.begin()+1, degOut.end()) - degOut.begin();
int maxIn = max_element(degIn.begin()+1, degIn.end()) - degIn.begin();
seeds.push_back(maxOut);
seeds.push_back(maxIn);
// add some random seeds
uniform_int_distribution<int> distNode(1, n);
for (int i = 0; i < 8 && (int)seeds.size() < 25; ++i) seeds.push_back(distNode(rng));
// deduplicate seeds
sort(seeds.begin(), seeds.end());
seeds.erase(unique(seeds.begin(), seeds.end()), seeds.end());
vector<int> visStamp(n+1, 0);
int stamp = 1;
vector<int> bestPath;
bestPath.reserve(n);
auto attempt = [&](int s)->vector<int> {
vector<int> pathVec;
pathVec.reserve(n);
deque<int> dq;
int head, tail;
int curStamp = stamp++;
if (curStamp == 0) { // overflow safety, unlikely
fill(visStamp.begin(), visStamp.end(), 0);
curStamp = ++stamp;
}
dq.clear();
dq.push_back(s);
visStamp[s] = curStamp;
head = tail = s;
while (true) {
bool extended = false;
// try extend tail via outgoing edges
{
int t = tail;
auto &vo = out[t];
for (int v : vo) {
if (visStamp[v] != curStamp) {
dq.push_back(v);
visStamp[v] = curStamp;
tail = v;
extended = true;
break;
}
}
}
if (extended) continue;
// try extend head via incoming edges
{
int h = head;
auto &vi = in[h];
for (int u : vi) {
if (visStamp[u] != curStamp) {
dq.push_front(u);
visStamp[u] = curStamp;
head = u;
extended = true;
break;
}
}
}
if (!extended) break;
}
pathVec.assign(dq.begin(), dq.end());
return pathVec;
};
auto startTime = chrono::steady_clock::now();
const double timeLimit = 3.5; // seconds, keep under 4s
for (int s : seeds) {
auto cur = attempt(s);
if (cur.size() > bestPath.size()) bestPath.swap(cur);
auto now = chrono::steady_clock::now();
double elapsed = chrono::duration<double>(now - startTime).count();
if (elapsed > timeLimit) break;
}
// If nothing found (shouldn't happen), pick any node
if (bestPath.empty()) bestPath.push_back(1);
// Output
cout << bestPath.size() << "\n";
for (size_t i = 0; i < bestPath.size(); ++i) {
if (i) cout << ' ';
cout << bestPath[i];
}
cout << "\n";
return 0;
} |