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vector<vector<double>> dist; // Entfernungen zwischen Punkten.
vector<vector<double>> dp;
double get(int p1, int p2) {
int v = max(p1, p2) + 1;
if (v == ssize(dist)) return dist[p1][v - 1] + dist[p2][v - 1];
if (dp[p1][p2] >= 0.0) return dp[p1][p2];
double tryLR = dist[p1][v] + get(v, p2);
double tryRL = dist[p2][v] + get(p1, v);
return dp[p1][p2] = min(tryLR, tryRL);
}
auto bitonicTSP() {
dp = vector<vector<double>>(ssize(dist),
vector<double>(ssize(dist), -1));
get(0, 0);
// return dp[0][0]; // Länge der Tour
vector<int> lr = {0}, rl = {0};
for (int p1 = 0, p2 = 0, v;
(v = max(p1, p2)+1) < ssize(dist);) {
if (dp[p1][p2] == dist[p1][v] + dp[v][p2]) {
lr.push_back(v); p1 = v;
} else {
rl.push_back(v); p2 = v;
}}
lr.insert(lr.end(), rl.rbegin(), rl.rend());
// Enthält Knoten 0 zweimal. An erster und letzter Position.
return lr;
}
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