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https://github.com/Kiritow/OJ-Problems-Source.git
synced 2024-03-22 13:11:29 +08:00
65 lines
1.8 KiB
C++
65 lines
1.8 KiB
C++
#include <cstdio>
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#include <cmath>
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#include <cstdlib>
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using namespace std;
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template<class T> inline void checkmax(T &a, T b)
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{if (b > a) a = b;}
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template<class T> inline void checkmin(T &a, T b)
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{if (b < a) a = b;}
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inline double sqr(double x)
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{return x * x;}
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struct Point {
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double x, y;
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} pt[35];
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int n;
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double tx, ty, v, c, sx, sy, dx, dy;
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double get(double p)
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{
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double cx = sx + dx * p;
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double cy = sy + dy * p;
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double cur = cy / v + sqrt(sqr(cx - tx) + sqr(cy - ty)) / c;
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return cur;
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}
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int ansidx;
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double ansp;
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void work()
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{
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for (int i = 1; i <= n; ++i) scanf("%lf%lf", &pt[i].x, &pt[i].y);
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pt[n + 1] = pt[1];
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double ans = 1e9;
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for (int i = 1; i <= n; ++i) {
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dx = pt[i + 1].x - pt[i].x;
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dy = pt[i + 1].y - pt[i].y;
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sx = pt[i].x;
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sy = pt[i].y;
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for (int iter = 1; iter <= 35; ++iter) {
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double p = 0;
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for (double len = 1; len > 1e-9; len /= 1.5) for (int iter1 = 1; iter1 <= 35; ++iter1) {
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if (rand() & 1) p += len; else p -= len;
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checkmax(p, 0.0);
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checkmin(p, 1.0);
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double tmp = get(p);
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if (tmp < ans) {
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ans = tmp;
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ansidx = i;
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ansp = p;
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}
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}
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}
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}
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double trueans = ans;
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ansp -= 5000 * 1e-7;
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for (int i = 0; i < 10000; ++i, ansp += 1e-7) {
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dx = pt[ansidx + 1].x - pt[ansidx].x;
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dy = pt[ansidx + 1].y - pt[ansidx].y;
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sx = pt[ansidx].x;
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sy = pt[ansidx].y;
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if (ansp > -1e-7 && ansp < 1 + 1e-7) checkmin(trueans, get(ansp));
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}
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printf("%0.4lf\n", trueans);
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}
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int main()
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{
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while (scanf("%d%lf%lf%lf%lf", &n, &tx, &ty, &v, &c), n) work();
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}
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