这里只给出代码，感兴趣的可以作以参考：
#include <algorithm> #include <cstdio> #include <cstring> #include <string> #include <queue> #include <map> #include <set> #include <stack> #include <ctime> #include <functional> #include <cmath> #include <iostream> #include <assert.h> #pragma comment(linker, "/STACK:102400000,102400000") #define max(a, b) ((a) > (b) ? (a) : (b)) #define min(a, b) ((a) < (b) ? (a) : (b)) #define mp std :: make_pair #define st first #define nd second #define keyn (root->ch[1]->ch[0]) #define lson (u << 1) #define rson (u << 1 | 1) #define pii std :: pair<int, int> #define pll pair<ll, ll> #define pb push_back #define type(x) __typeof(x.begin()) #define foreach(i, j) for(type(j)i = j.begin(); i != j.end(); i++) #define FOR(i, s, t) for(int i = (s); i <= (t); i++) #define ROF(i, t, s) for(int i = (t); i >= (s); i--) #define dbg(x) std::cout << x << std::endl #define dbg2(x, y) std::cout << x << " " << y << std::endl #define clr(x, i) memset(x, (i), sizeof(x)) #define maximize(x, y) x = max((x), (y)) #define minimize(x, y) x = min((x), (y)) using namespace std; typedef long long ll; const int int_inf = 0x3f3f3f3f; const ll ll_inf = 0x3f3f3f3f3f3f3f3f; const int INT_INF = (int)((1ll << 31) - 1); const double double_inf = 1e30; const double eps = 1e-14; const double pi = acos(-1.); typedef unsigned long long ul; typedef unsigned int ui; inline int readint() { int x; scanf("%d", &x); return x; } inline int readstr(char *s) { scanf("%s", s); return strlen(s); } class cmpt { public: bool operator () (const int &x, const int &y) const { return x > y; } }; int Rand(int x, int o) { //if o set, return [1, x], else return [0, x - 1] if (!x) return 0; int tem = (int)((double)rand() / RAND_MAX * x) % x; return o ? tem + 1 : tem; } ll ll_rand(ll x, int o) { if (!x) return 0; ll tem = (ll)((double)rand() / RAND_MAX * x) % x; return o ? tem + 1 : tem; } void data_gen() { srand(time(0)); freopen("in.txt", "w", stdout); int kases = 100; //printf("%d ", kases); while (kases--) { int L = Rand(1000, 1) + 5; int n = Rand(L - 4, 1) + 3; int buf[1500], p = 0; FOR(i, 1, n) buf[i] = Rand(L, 0); buf[++n] = 0, buf[++n] = L; sort(buf + 1, buf + n + 1); n = unique(buf + 1, buf + n + 1) - buf - 1; printf("%d %d ", L, n); int t1 = Rand(13, 0) + 6; int t2 = Rand(13, 0) + 6; while (t2 == t1) { t2 = Rand(13, 0) + 6; } if (t1 > t2) swap(t1, t2); printf("%d %d ", t1, t2); FOR(i, 1, n) { printf("%d %d ", buf[i], Rand(1000, 1)); } puts(" "); } puts("0 0"); } const int maxn = 1e3 + 10; pii a[maxn]; int n, L; int t1, t2; struct Line { int lhs, rhs; double theta; int o; Line() {} Line(int _lhs, int _rhs, double _ta, int _o) { lhs = _lhs, rhs = _rhs, theta = _ta, o = _o; } bool operator < (const Line &other) { return theta > other.theta || theta == other.theta && rhs > other.rhs || theta == other.theta && rhs == other.rhs && lhs > other.lhs; } }lines[maxn * maxn]; int k; double shadow, H; bool inq[maxn]; double cal(double theta1, double theta2) { if (abs(theta1 - theta2) < eps) return 0; double X = abs(theta1 - pi / 2) < eps ? 0 : H / tan(theta1); double ret = (cos(theta2) - cos(theta1)) * (L - shadow + X) - H * (sin(theta1) - sin(theta2)); shadow += abs(theta2) < eps ? L - shadow : H / tan(theta2) - X; return ret; } double solve(int l, int r) { shadow = H = 0; k = 0; FOR(i, 2, n) { inq[i] = 1; H += a[i].nd; double mini = (double)ll_inf; int mk = 0; ROF(j, i - 1, 1) { double ang_tan = (double)a[i].second / (a[i].first - a[j].first); lines[k++] = Line(j, i, atan(ang_tan), 0); if (a[i].second <= a[j].second) break; ang_tan = (double)(a[i].second - a[j].second) / (a[i].first - a[j].first); lines[k++] = Line(j, i, atan(ang_tan), 1); } } double ang_l = pi / 12 * (18 - l), ang_r = pi / 12 * (18 - r); lines[k++] = Line(0, 0, ang_l, 2), lines[k++] = Line(0, 0, ang_r, 3); sort(lines, lines + k); double ans = 0; bool okay = false; double pre = pi / 2; FOR(i, 0, k - 1) { int o = lines[i].o; int lhs = lines[i].lhs, rhs = lines[i].rhs; double ang = lines[i].theta; double res = cal(pre, ang); if (okay) ans += res; if (o == 3) break; else if (o == 2) okay = true; else if (o == 0 && inq[rhs]) inq[rhs] = 0, H -= a[rhs].nd, mk = 1; else if (o == 1 && inq[lhs]) H += a[rhs].nd - a[lhs].nd, inq[lhs] = 0, inq[rhs] = 1, mk = 1; pre = ang; } return abs(ans * 12 / pi); } int main() { //data_gen(); return 0; //C(); return 0; int debug = 0; if (debug) freopen("in.txt", "r", stdin); //freopen("out.txt", "w", stdout); int kases = 0; while (~scanf("%d%d", &L, &n) && n) { ++kases; t1 = readint(), t2 = readint(); FOR(i, 1, n) scanf("%d%d", &a[i].st, &a[i].nd); double ans = 0; if (t1 >= 12) ans += solve(t1, t2); else { if (t2 > 12) ans += solve(12, t2), t2 = 12; FOR(i, 1, n) a[i].first = L - a[i].st; FOR(i, 1, n / 2) swap(a[i], a[n + 1 - i]); ans += solve(24 - t2, 24 - t1); } printf("%.5f ", ans); } return 0; }