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  1. #include <bits/stdc++.h>
  2. #include "jngen.h"
  3. using namespace std;
  4. #define forn(i, n) for (int i = 0; i < int(n); ++i)
  5.  
  6. jngen::Dsu dsu;
  7.  
  8. int n = 1000;
  9. vector<Point> p;
  10.  
  11. double dist(Point x, Point y) {
  12.     double dx = x.x - y.x;
  13.     double dy = x.y - y.y;
  14.     return sqrt(dx*dx+dy*dy);
  15. }
  16.  
  17. vector<vector<int>> e;
  18. vector<int> b;
  19. vector<int> res;
  20.  
  21. void dfs(int v) {
  22.     b[v] = 1;
  23.     res.push_back(v);
  24.     for (int to: e[v]) {
  25.         if (!b[to]) dfs(to);
  26.     }
  27. }
  28.  
  29. bool intersect(int l1, int r1, int l2, int r2) {
  30.     return max(l1, l2) <= min(r1, r2);
  31. }
  32.  
  33. bool segmentsIntersect(Point a, Point b, Point c, Point d) {
  34.     if (!intersect(min(a.x, b.x), max(a.x, b.x), min(c.x, d.x), max(c.x, d.x))) return false;
  35.     if (!intersect(min(a.y, b.y), max(a.y, b.y), min(c.y, d.y), max(c.y, d.y))) return false;
  36.     for (int i = 0; i < 2; ++i) {
  37.         long long s1 = (c-a) % (b-a);
  38.         long long s2 = (d-a) % (b-a);
  39.         assert(s1 != 0 && s2 != 0);
  40.         if ((s1 < 0) == (s2 < 0)) return false;
  41.     }
  42.     return true;
  43. }
  44.  
  45. vector<Point> runFix(vector<Point> p) {
  46.     bool done = true;
  47.     int n = p.size();
  48.     while (done) {
  49.         cerr << "Fixing..." << endl;
  50.         done = false;
  51.         for (int i = 0; i < n; ++i) {
  52.             for (int j = i+2; j < n; ++j) {
  53.                 if ((j+1)%n == i) continue;
  54.                 if (segmentsIntersect(p[i], p[i+1], p[j], p[(j+1)%n])) {
  55.                     reverse(p.begin() + i + 1, p.begin() + j + 1);
  56.                     done = true;
  57.                 }
  58.             }
  59.         }
  60.     }
  61.     return p;
  62. }
  63.  
  64. int main(int argc, char *argv[]) {
  65.     // registerGen(argc, argv);
  66.     parseArgs(argc, argv);
  67.  
  68.     p = rndg.pointsInGeneralPosition(n, 100000).shuffled();
  69.     vector<pair<int, int>> es;
  70.     forn(i, n) forn(j, i) es.emplace_back(i, j);
  71.     sort(es.begin(), es.end(), [&](pair<int, int> x, pair<int, int> y) {
  72.         return dist(p[x.first], p[x.second]) < dist(p[y.first], p[y.second]);
  73.     });
  74.     e.resize(n);
  75.     b.resize(n);
  76.     for (auto ee: es) {
  77.         int x, y;
  78.         tie(x, y) = ee;
  79.         if (dsu.unite(x, y)) {
  80.             e[x].push_back(y);
  81.             e[y].push_back(x);
  82.         }
  83.     }
  84.     mt19937 rr;
  85.     forn(i, n) shuffle(e[i].begin(), e[i].end());
  86.     dfs(0);
  87.  
  88.     // Uncomment this line to try random order instead of MST order.
  89.     // res = Array::id(n).shuffle();
  90.  
  91.     res.push_back(res[0]);
  92.  
  93.     Drawer d;
  94.     for (auto pp: p) d.point(pp);
  95.     forn(i, n) d.segment(p[res[i]], p[res[i+1]]);
  96.     d.dumpSvg("image.svg");
  97.  
  98.     vector<Point> fixed;
  99.     forn(i, n) fixed.push_back(p[res[i]]);
  100.     fixed = runFix(fixed);
  101.  
  102.     d = Drawer();
  103.     for (auto pp: p) d.point(pp);
  104.     forn(i, n) d.segment(fixed[i], fixed[(i+1)%n]);
  105.     d.dumpSvg("image_fixed.svg");
  106. }
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