Submission #906115

#	Time	Username	Problem	Language	Result	Execution time	Memory
906115		belgianbot	Mobile (BOI12_mobile)	C++14	8 / 100	423 ms	10596 KiB

mobile

#include <bits/stdc++.h>
#define pow(x, y) (long double)(pow(x, y))
using namespace std;

struct coord{
	int x, y;
};

vector <coord> a;
int N, L;
/*long double dis(int ax, ay, long double ans) {
	return (long double)(sqrt(pow(ay, 2) + pow(ax - ans, 2)));
}
long double distance(int i, int j) {
	long long num = pow(a[i].y, 2) - pow(a[j].y, 2) - pow(a[j].x, 2) + pow(a[i].x, 2);
	long long den = 2 * (-a[j].x + a[i].x);
	
	if (den == 0) return sqrt(num);
	long double frac = (long double)(num) / (long double)(den);
	
	return frac;
}*/
bool solve(long double mid) {
	long double right(0);
	for (int i(0); i < a.size(); i++) {
		if (abs(a[i].y) > mid) continue;
		long double iLeft = (long double)(a[i].x) - (long double)(sqrt(pow(mid, 2) - pow(a[i].y, 2)));
		long double iRight = a[i].x + (a[i].x - iLeft);
		if (iLeft <= right) right = max(right,iRight);
	}
	return (right >= L);
}
int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin >> N >> L;
	
	a.clear();
	int x, y; cin >> x >> y;
	a.push_back({x, y});
	for (int i(0); i < N - 1; i++) {
		int ax, ay;
		cin >> ax >> ay;
		a.push_back({ax, ay});
	}
	long double l(0), r(1e9);
	long double ans(0);
	while (r - l > 0.00001) {
		long double mid = l + (r - l) / 2;
		
		if (solve(mid)){
			 r = mid;
			 ans = r;
		 }
		else l = mid;
	}
	cout << l << '\n';
	return 0;
}

Compilation message (stderr)

mobile.cpp: In function 'bool solve(long double)':
mobile.cpp:25:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<coord>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   25 |  for (int i(0); i < a.size(); i++) {
      |                 ~~^~~~~~~~~~
mobile.cpp: In function 'int main()':
mobile.cpp:47:14: warning: variable 'ans' set but not used [-Wunused-but-set-variable]
   47 |  long double ans(0);
      |              ^~~

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