104 lines
2.2 KiB
C++
104 lines
2.2 KiB
C++
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#include <algorithm>
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#include <climits>
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#include <vector>
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#include <iostream>
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using namespace std;
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typedef pair<int, int> pii;
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typedef vector<pii> vpii;
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const int maxn = 100000;
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int tx[maxn];
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int ty[maxn];
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bool divX[maxn];
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bool cmpX(const pii &a, const pii &b) {
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return a.first < b.first;
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}
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bool cmpY(const pii &a, const pii &b) {
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return a.second < b.second;
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}
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void buildTree(int left, int right, pii points[]) {
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if (left >= right)
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return;
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int mid = (left + right) >> 1;
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//sort(points + left, points + right + 1, divX ? cmpX : cmpY);
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int minx = INT_MAX;
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int maxx = INT_MIN;
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int miny = INT_MAX;
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int maxy = INT_MIN;
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for (int i = left; i < right; i++) {
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checkmin(minx, points[i].first);
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checkmax(maxx, points[i].first);
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checkmin(miny, points[i].second);
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checkmax(maxy, points[i].second);
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}
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divX[mid] = (maxx - minx) >= (maxy - miny);
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nth_element(points + left, points + mid, points + right, divX[mid] ? cmpX : cmpY);
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tx[mid] = points[mid].first;
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ty[mid] = points[mid].second;
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if (left + 1 == right)
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return;
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buildTree(left, mid, points);
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buildTree(mid + 1, right, points);
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}
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long long closestDist;
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int closestNode;
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void findNearestNeighbour(int left, int right, int x, int y) {
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if (left >= right)
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return;
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int mid = (left + right) >> 1;
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int dx = x - tx[mid];
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int dy = y - ty[mid];
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long long d = dx * (long long) dx + dy * (long long) dy;
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if (closestDist > d && d) {
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closestDist = d;
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closestNode = mid;
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}
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if (left + 1 == right)
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return;
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int delta = divX[mid] ? dx : dy;
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long long delta2 = delta * (long long) delta;
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int l1 = left;
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int r1 = mid;
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int l2 = mid + 1;
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int r2 = right;
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if (delta > 0)
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swap(l1, l2), swap(r1, r2);
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findNearestNeighbour(l1, r1, x, y);
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if (delta2 < closestDist)
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findNearestNeighbour(l2, r2, x, y);
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}
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int findNearestNeighbour(int n, int x, int y) {
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closestDist = LLONG_MAX;
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findNearestNeighbour(0, n, x, y);
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return closestNode;
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}
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int main() {
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vpii p;
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p.push_back(make_pair(0, 2));
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p.push_back(make_pair(0, 3));
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p.push_back(make_pair(-1, 0));
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p.resize(unique(p.begin(), p.end()) - p.begin());
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int n = p.size();
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buildTree(1, 0, n - 1, &(vpii(p)[0]));
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int res = findNearestNeighbour(n, 0, 0);
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cout << p[res].first << " " << p[res].second << endl;
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return 0;
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}
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