60 lines
1.9 KiB
C++
60 lines
1.9 KiB
C++
#include <iostream>
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#include <vector>
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#include <cmath>
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#include <algorithm>
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using namespace std;
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double other_leg(const double leg, const double diag) {
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return sqrt(diag * diag - leg * leg);
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}
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double diag(const double leg1, const double leg2) {
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return sqrt(leg1 * leg1 + leg2 * leg2);
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}
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vector<pair<double, double>> target_ranges(vector<pair<int, int>> islands, const int distance) {
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vector<pair<double, double>> ranges;
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for (auto& [island_x, island_y] : islands) {
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if (island_y > distance) { throw std::runtime_error("Island is too far away from the radar."); }
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const double offset = other_leg(island_y, distance);
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ranges.emplace_back(island_x - offset, island_x + offset);
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}
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sort(ranges.begin(), ranges.end(),
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[](const auto& a, const auto& b) { return a.second < b.second; });
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return ranges;
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}
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int required_radars(const vector<pair<double, double>>& ranges) {
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if (ranges.empty()) { return 0; }
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int answer = 1;
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double current_max_x = ranges[0].second;
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for (const auto& [left,right] : ranges) {
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if (left > current_max_x) { answer++, current_max_x = right; } // 放不下，加雷达
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else if (right < current_max_x) { current_max_x = right; } // 放下，需要左移雷达
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clog << "current_max_x: " << current_max_x << " answer: " << answer << endl;
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}
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return answer;
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}
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int main() {
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ios::sync_with_stdio(false);
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cin.tie(nullptr);
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int n, distance, case_id = 0;
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while (cin >> n >> distance) {
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if (n == 0 && distance == 0) { break; }
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vector<pair<int, int>> islands(n);
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for (int i = 0; i < n; i++) {
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cin >> islands[i].first >> islands[i].second;
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}
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// cout << "Case " << ++case_id << ": ";
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try {
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cout << required_radars(target_ranges(islands, distance)) << endl;
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} catch (std::runtime_error&) {
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cout << -1 << endl;
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}
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}
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}
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