求多边形重心

ACM模版

求多边形重心

/* *  求多边形重心 *  INIT: pnt[]已按顺时针(或逆时针)排好序; | CALL: res = bcenter(pnt, n); */struct point{    double x, y;};point bcenter(point pnt[], int n){    point p, s;    double tp, area = 0, tpx = 0, tpy = 0;    p.x = pnt[0].x;    p.y = pnt[0].y;    for (int i = 1; i <= n; ++i)    {   //  point:0 ~ n - 1        s.x = pnt[(i == n) ? 0 : i].x;        s.y = pnt[(i == n) ? 0 : i].y;        tp = (p.x * s.y - s.x * p.y);        area += tp / 2;        tpx += (p.x + s.x) * tp;        tpy += (p.y + s.y) * tp;        p.x = s.x;        p.y = s.y;    }    s.x = tpx / (6 * area);    s.y = tpy / (6 * area);    return s;}