uva 1077 - The Sky is the Limit（离散化）

题目链接：uva 1077 - The Sky is the Limit

代码

#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>using namespace std;const int maxn = 200005;const double eps = 1e-8;struct Point {    double x, y;    Point(double x = 0, double y = 0): x(x), y(y) {}    Point operator + (const Point& u) { return Point(x+u.x, y+u.y); }    Point operator - (const Point& u) { return Point(x-u.x, y-u.y); }    Point operator * (const double& k) { return Point(x*k, y*k); }};typedef Point Vector;inline double dcmp(double x) { if (fabs(x) < eps) return 0; else return x < 0 ? -1 : 1; }double getCross(Vector a, Vector b) { return a.x * b.y - a.y * b.x; }double getDot(Vector a, Vector b) { return a.x * b.x + a.y * b.y; }double getLength(Vector a) { return sqrt(getDot(a, a)); }/* 判断线段是否存在交点 */bool haveIntersection (Point a1, Point a2, Point b1, Point b2) {    double c1=getCross(a2-a1, b1-a1), c2=getCross(a2-a1, b2-a1), c3=getCross(b2-b1, a1-b1), c4=getCross(b2-b1,a2-b1);    return dcmp(c1)*dcmp(c2) < 0 && dcmp(c3)*dcmp(c4) < 0;}/* 直线pv和直线qw的交点 */bool getIntersection (Point p, Vector v, Point q, Vector w, Point& o) {    if (dcmp(getCross(v, w)) == 0) return false;    Vector u = p - q;    double k = getCross(w, u) / getCross(v, w);    o = p + v * k;    return true;}int N, C;double X[maxn];Point L[maxn][2], R[maxn][2];void init () {    C = 0;    double x, h, b;    for (int i = 0; i < N; i++) {        scanf("%lf%lf%lf", &x, &h, &b);        X[C++] = x - b * 0.5;        X[C++] = x;        X[C++] = x + b * 0.5;        L[i][0] = Point(x - b * 0.5, 0);        R[i][0] = L[i][1] = Point(x, h);        R[i][1] = Point(x + b * 0.5, 0);    }    Point tmp;    for (int i = 0; i < N; i++) {        for (int ki = 0; ki < 2; ki++) {            for (int j = i+1; j < N; j++) {                for (int kj = 0; kj < 2; kj++) {                    if (haveIntersection (L[i][ki], R[i][ki], L[j][kj], R[j][kj])) {                        getIntersection (L[i][ki], R[i][ki]-L[i][ki], L[j][kj], R[j][kj]-L[j][kj], tmp);                        X[C++] = tmp.x;                    }                }            }        }    }}double find (double x) {    double ret = 0;    Point tmp;    for (int i = 0; i < N; i++) {        for (int j = 0; j < 2; j++) {            if (dcmp(L[i][j].x -  x) <= 0 && dcmp(x - R[i][j].x) <= 0) {                //double haha = L[i][j].y + (x - L[i][j].x) / (R[i][j].x - L[i][j].x) * (R[i][j].y - L[i][j].y);                getIntersection(L[i][j], R[i][j]-L[i][j], Point(x, 0), Vector(0, 1), tmp);                ret = max(ret, tmp.y);            }        }    }    return ret;}double solve () {    sort(X, X + C);    C = unique(X, X + C) - X;    double ans = 0, pre = find(X[0]);    for (int i = 1; i < C; i++) {        double cur = find(X[i]);        if (dcmp(cur) > 0 || dcmp(pre) > 0)            ans += getLength(Point(X[i], cur) - Point(X[i-1], pre));        pre = cur;    }    return ans;}int main () {    int cas = 1;    while (scanf("%d", &N) == 1 && N) {        init();        printf("Case %d: %.0lf\n\n", cas++, solve());    }    return 0;}