Submission #1045642

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
1045642	2024-08-06T06:41:10 Z	VectorLi	Mobile (BOI12_mobile)	C++17	0 / 100	449 ms	8268 KB

mobile

#include <bits/stdc++.h>
#define long long long

using namespace std;

const int N = (int) 1E6;

int n, k;
int x[N], y[N];

/*
为什么这么做的对的，考虑排序线段。
我们排序线段的目的就是为了 连的上！
所以如果线段 i 在 j 之后出现
且 l(i) < l(j)
一定有 r(i) > r(j)，这就保证了我们不需要使用排序 
*/

bool valid(double a) {
	double t = 0;
	// t 表示已经可以覆盖 [0, t] 了，初始为空区间 
	// 因为输入的点的坐标是有序的，所以如果当前的 r 只能覆盖线段
	// 的中段的话，t 还会保持是 0 
	for (int i = 0; i < n; i++) {
		double l = x[i] - sqrt(1.0 * a * a - 1.0 * y[i] * y[i]);
		// 直接 y[i] * y[i] 可能会爆
		// 同时，由于 r 大于最大的 abs(y[i])，所以不会出现 sqrt 负数的情况 
		double r = x[i] + sqrt(1.0 * a * a - 1.0 * y[i] * y[i]);
		if (l <= t && r >= t) {
			t = r;
		}
	}
	return t >= k;
}

void solve() {
	cin >> n >> k;
	for (int i = 0; i < n; i++) {
		cin >> x[i] >> y[i];
	}
	
	double l = 0, r = 2E9;
	for (int i = 0; i < n; i++) {
		l = max(l, 1.0 * abs(y[i]));
	}
	for (int i = 0; i < 100; i++) {
		double m = (l + r) / 2;
		if (valid(m)) {
			r = m;
		} else {
			l = m;
		}
	}
	cout << fixed << setprecision(6);
	cout << r << "\n";
}

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int t;
	t = 1;
	for (int i = 0; i < t; i++) {
		solve();
	}
	return 0;
}

Subtask #1
0 / 4.0

#	Verdict	Execution time	Memory	Grader output
1	Incorrect	0 ms	2392 KB	Output isn't correct
2	Halted	0 ms	0 KB	-

Subtask #2
0 / 4.0

#	Verdict	Execution time	Memory	Grader output
1	Incorrect	0 ms	2396 KB	Output isn't correct
2	Halted	0 ms	0 KB	-

Subtask #3
0 / 4.0

#	Verdict	Execution time	Memory	Grader output
1	Incorrect	1 ms	2392 KB	Output isn't correct
2	Halted	0 ms	0 KB	-

Subtask #4
0 / 4.0

#	Verdict	Execution time	Memory	Grader output
1	Incorrect	3 ms	2396 KB	Output isn't correct
2	Halted	0 ms	0 KB	-

Subtask #5
0 / 4.0

#	Verdict	Execution time	Memory	Grader output
1	Incorrect	2 ms	2396 KB	Output isn't correct
2	Halted	0 ms	0 KB	-

Subtask #6
0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	3 ms	2520 KB	Output is correct
2	Correct	2 ms	2396 KB	Output is correct
3	Incorrect	2 ms	2396 KB	Output isn't correct
4	Halted	0 ms	0 KB	-

Subtask #7
0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Incorrect	26 ms	4748 KB	Output isn't correct
2	Halted	0 ms	0 KB	-

Subtask #8
0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Incorrect	27 ms	4720 KB	Output isn't correct
2	Halted	0 ms	0 KB	-

Subtask #9
0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	38 ms	4700 KB	Output is correct
2	Correct	39 ms	4700 KB	Output is correct
3	Incorrect	29 ms	4696 KB	Output isn't correct
4	Halted	0 ms	0 KB	-

Subtask #10
0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	47 ms	6748 KB	Output is correct
2	Correct	46 ms	6744 KB	Output is correct
3	Incorrect	37 ms	6744 KB	Output isn't correct
4	Halted	0 ms	0 KB	-

Subtask #11
0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	37 ms	6748 KB	Output is correct
2	Correct	46 ms	6748 KB	Output is correct
3	Incorrect	33 ms	6744 KB	Output isn't correct
4	Halted	0 ms	0 KB	-

Subtask #12
0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	166 ms	6992 KB	Output is correct
2	Correct	178 ms	6748 KB	Output is correct
3	Correct	173 ms	6748 KB	Output is correct
4	Incorrect	185 ms	6780 KB	Output isn't correct
5	Halted	0 ms	0 KB	-

Subtask #13
0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	217 ms	6748 KB	Output is correct
2	Incorrect	170 ms	6744 KB	Output isn't correct
3	Halted	0 ms	0 KB	-

Subtask #14
0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	199 ms	7000 KB	Output is correct
2	Correct	220 ms	6748 KB	Output is correct
3	Correct	214 ms	6744 KB	Output is correct
4	Incorrect	225 ms	7000 KB	Output isn't correct
5	Halted	0 ms	0 KB	-

Subtask #15
0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	219 ms	6744 KB	Output is correct
2	Incorrect	249 ms	6800 KB	Output isn't correct
3	Halted	0 ms	0 KB	-

Subtask #16
0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	232 ms	6992 KB	Output is correct
2	Correct	243 ms	7056 KB	Output is correct
3	Correct	240 ms	6992 KB	Output is correct
4	Incorrect	287 ms	7032 KB	Output isn't correct
5	Halted	0 ms	0 KB	-

Subtask #17
0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	245 ms	6992 KB	Output is correct
2	Incorrect	245 ms	6864 KB	Output isn't correct
3	Halted	0 ms	0 KB	-

Subtask #18
0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	314 ms	7300 KB	Output is correct
2	Correct	280 ms	7288 KB	Output is correct
3	Correct	293 ms	7340 KB	Output is correct
4	Incorrect	301 ms	7248 KB	Output isn't correct
5	Halted	0 ms	0 KB	-

Subtask #19
0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	289 ms	7484 KB	Output is correct
2	Incorrect	275 ms	7252 KB	Output isn't correct
3	Halted	0 ms	0 KB	-

Subtask #20
0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	333 ms	8072 KB	Output is correct
2	Correct	362 ms	8056 KB	Output is correct
3	Correct	353 ms	8068 KB	Output is correct
4	Incorrect	449 ms	8268 KB	Output isn't correct
5	Halted	0 ms	0 KB	-

Subtask #21
0 / 5.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	360 ms	8056 KB	Output is correct
2	Incorrect	371 ms	8260 KB	Output isn't correct
3	Halted	0 ms	0 KB	-

Submission #1045642

Compilation message