#include <bits/stdc++.h> using namespace std; struct Car { int pos; bool starts; }; typedef long double dbl_t; constexpr dbl_t eps = 1e-10; vector<Car> cars[4]; int v[4]; vector<Car> ReadLine(int L) { vector<Car> l; char buf[L + 8]; scanf("%s", buf); buf[0] = '.'; buf[L] = '.'; for (int i = 1; i <= L; ++i) if (buf[i] != buf[i - 1]) { bool starts = buf[i] == '#'; l.push_back(Car{i - starts, starts}); } reverse(l.begin(), l.end()); return l; } struct Simulation { dbl_t pos[4]; dbl_t& t = pos[0]; bool blocked[4]; bool event[4]; dbl_t dt; void TrySchedule(int i, int j) { int agent_speed = blocked[i] ? v[i] : v[0]; if (agent_speed <= v[j]) return; if (cars[j].back().starts != (i == j)) return; dbl_t dist = cars[j].back().pos + t * v[j] - pos[i]; dbl_t dt_cand = dist / (agent_speed - v[j]); if (dt_cand < dt - eps) for (int k = 1; k <= 3; ++k) event[k] = false; if (dt_cand <= dt + eps) { dt = dt_cand; event[j] = true; } } void Fix(int i, dbl_t new_pos) { while (!cars[i].empty()) { dbl_t p = cars[i].back().pos + v[i] * t; dbl_t new_pos_for_1 = p; if (cars[i].back().starts) p += eps; else p -= eps; if (p > new_pos) break; blocked[i] = cars[i].back().starts; if (i == 1 && blocked[i]) pos[1] = new_pos_for_1; cars[i].pop_back(); } if (!blocked[i]) pos[i] = new_pos; } void NextEvent() { dt = numeric_limits<dbl_t>::max(); for (int j = 1; j <= 3; ++j) { if (!cars[j].empty()) for (int i = 1; i <= 3; ++i) if (abs(i - j) <= 1) TrySchedule(i, j); } for (int i = 1; i <= 3; ++i) pos[i] += (blocked[i] ? v[i] : v[0]) * dt; t += dt; for (int j = 1; j <= 3; ++j) if (event[j]) { blocked[j] = cars[j].back().starts; cars[j].pop_back(); } if (event[1] && !blocked[1]) pos[1] = pos[2]; if (event[3] && !blocked[3]) pos[3] = pos[2]; if (event[2] && !blocked[2]) { if (pos[1] == pos[3]) pos[2] = pos[1]; else if (pos[1] > pos[3]) { pos[2] = pos[1]; Fix(3, pos[2]); } else { pos[2] = pos[3]; Fix(1, pos[2]); } } /* printf("t=%.9Lg:", t); for (int i = 1; i <= 3; ++i) printf(" %.9Lg%c", pos[i], blocked[i] ? '[' : '>'); printf("\n"); */ } void Run() { for (int i = 0; i < 4; ++i) { pos[i] = 0.0; blocked[i] = false; } for (;;) { bool empty = true; for (int i = 1; i <= 3; i++) empty &= cars[i].empty(); if (empty) break; NextEvent(); } } }; int main() { int L; scanf("%d", &L); for (int i = 0; i < 4; ++i) scanf("%d", v + i); dbl_t v2 = v[2]; for (int i = 0; i < 4; ++i) v[i] -= v2; for (int i = 1; i <= 3; ++i) cars[i] = ReadLine(L); Simulation s; s.Run(); printf("%.15Lf\n", s.t); return 0; }
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 | #include <bits/stdc++.h> using namespace std; struct Car { int pos; bool starts; }; typedef long double dbl_t; constexpr dbl_t eps = 1e-10; vector<Car> cars[4]; int v[4]; vector<Car> ReadLine(int L) { vector<Car> l; char buf[L + 8]; scanf("%s", buf); buf[0] = '.'; buf[L] = '.'; for (int i = 1; i <= L; ++i) if (buf[i] != buf[i - 1]) { bool starts = buf[i] == '#'; l.push_back(Car{i - starts, starts}); } reverse(l.begin(), l.end()); return l; } struct Simulation { dbl_t pos[4]; dbl_t& t = pos[0]; bool blocked[4]; bool event[4]; dbl_t dt; void TrySchedule(int i, int j) { int agent_speed = blocked[i] ? v[i] : v[0]; if (agent_speed <= v[j]) return; if (cars[j].back().starts != (i == j)) return; dbl_t dist = cars[j].back().pos + t * v[j] - pos[i]; dbl_t dt_cand = dist / (agent_speed - v[j]); if (dt_cand < dt - eps) for (int k = 1; k <= 3; ++k) event[k] = false; if (dt_cand <= dt + eps) { dt = dt_cand; event[j] = true; } } void Fix(int i, dbl_t new_pos) { while (!cars[i].empty()) { dbl_t p = cars[i].back().pos + v[i] * t; dbl_t new_pos_for_1 = p; if (cars[i].back().starts) p += eps; else p -= eps; if (p > new_pos) break; blocked[i] = cars[i].back().starts; if (i == 1 && blocked[i]) pos[1] = new_pos_for_1; cars[i].pop_back(); } if (!blocked[i]) pos[i] = new_pos; } void NextEvent() { dt = numeric_limits<dbl_t>::max(); for (int j = 1; j <= 3; ++j) { if (!cars[j].empty()) for (int i = 1; i <= 3; ++i) if (abs(i - j) <= 1) TrySchedule(i, j); } for (int i = 1; i <= 3; ++i) pos[i] += (blocked[i] ? v[i] : v[0]) * dt; t += dt; for (int j = 1; j <= 3; ++j) if (event[j]) { blocked[j] = cars[j].back().starts; cars[j].pop_back(); } if (event[1] && !blocked[1]) pos[1] = pos[2]; if (event[3] && !blocked[3]) pos[3] = pos[2]; if (event[2] && !blocked[2]) { if (pos[1] == pos[3]) pos[2] = pos[1]; else if (pos[1] > pos[3]) { pos[2] = pos[1]; Fix(3, pos[2]); } else { pos[2] = pos[3]; Fix(1, pos[2]); } } /* printf("t=%.9Lg:", t); for (int i = 1; i <= 3; ++i) printf(" %.9Lg%c", pos[i], blocked[i] ? '[' : '>'); printf("\n"); */ } void Run() { for (int i = 0; i < 4; ++i) { pos[i] = 0.0; blocked[i] = false; } for (;;) { bool empty = true; for (int i = 1; i <= 3; i++) empty &= cars[i].empty(); if (empty) break; NextEvent(); } } }; int main() { int L; scanf("%d", &L); for (int i = 0; i < 4; ++i) scanf("%d", v + i); dbl_t v2 = v[2]; for (int i = 0; i < 4; ++i) v[i] -= v2; for (int i = 1; i <= 3; ++i) cars[i] = ReadLine(L); Simulation s; s.Run(); printf("%.15Lf\n", s.t); return 0; } |