poj 2540 Hotter Colder

poj 2540 Hotter Colder

#include<stdio.h>#include<string.h>#define MAXD 210#define INF 10#define zero 1e-8struct point{    double x, y;}wa[MAXD], wb[MAXD], *a, *b;int N, na, nb;double px, py, cx, cy;char st[10];double fabs(double x){    return x < 0 ? -x : x;}int dcmp(double x){    return fabs(x) < zero ? 0 : (x < 0 ? -1 : 1);}double det(double x1, double y1, double x2, double y2){    return x1 * y2 - x2 * y1;}void init(){    int i, j, k;    a = wa, b = wb;    a[0].x = 0, a[0].y = 0, a[1].x = INF, a[1].y = 0, a[2].x = INF, a[2].y = INF, a[3].x = 0, a[3].y = INF;    a[na = 4] = a[0];    px = py = 0;}void add(double x, double y){    b[nb].x = x, b[nb].y = y;    ++ nb;}void cut(double x0, double y0, double nx, double ny){    int i, j, k;    point *t;    double t1, t2, x, y;    nb = 0;    for(i = 0; i < na; i ++)    {        t1 = det(nx, ny, a[i].x - x0, a[i].y - y0);        t2 = det(nx, ny, a[i + 1].x - x0, a[i + 1].y - y0);        if(dcmp(t1) >= 0) add(a[i].x, a[i].y);        if(dcmp(t1) * dcmp(t2) < 0)        { x = (fabs(t2) * a[i].x + fabs(t1) * a[i + 1].x) / (fabs(t1) + fabs(t2)); y = (fabs(t2) * a[i].y + fabs(t1) * a[i + 1].y) / (fabs(t1) + fabs(t2)); add(x, y);        }    }    t = a, a = b, b = t;    a[na = nb] = a[0];}void calculate(){    int i, j, k;    double s = 0;    for(i = 0; i < na; i ++)        s += det(a[i].x, a[i].y, a[i + 1].x, a[i + 1].y);    printf("%.2lfn", fabs(s) / 2);}void solve(){    int i, j, k;    if(st[0] == 'S')        na = 0;    else if(st[0] == 'H')        cut((px + cx) / 2, (py + cy) / 2, cy - py, px - cx);    else        cut((px + cx) / 2, (py + cy) / 2, py - cy, cx - px);    calculate();}int main(){    init();    while(scanf("%lf%lf%s", &cx, &cy, st) == 3)    {        solve();        px = cx, py = cy;    }    return 0;}