HDU 1348 (凸包)

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题意是求凸包的周长加上一个半径为l的圆周长。

板子题。

#include <bits/stdc++.h>using namespace std;typedef unsigned long long ll;#define maxn 1111#define pi acos (-1)struct point {    double x, y;    point (double _x = 0, double _y = 0) : x(_x), y(_y) {}    point operator - (point a) const {        return point (x-a.x, y-a.y);    }    bool operator < (const point &a) const {        return x < a.x || (x == a.x && y < a.y);    }}p[maxn];const double eps = 1e-10;int dcmp (double x) {    if (fabs (x) < eps)        return 0;    else return x < 0 ? -1 : 1;}double cross (point a, point b) {    return a.x*b.y-a.y*b.x;}double dot (point a, point b) {    return a.x*b.x + a.y*b.y;}int n, m;double l;point ch[maxn];int ConvexHull () {    sort (p, p+n);    int m = 0;    for (int i = 0; i < n; i++) {        while (m > 1 && cross (ch[m-1]-ch[m-2], p[i]-ch[m-1]) <= 0)            m--;        ch[m++] = p[i];    }    int k = m;    for (int i = n-2; i >= 0; i--) {        while (m > k && cross (ch[m-1]-ch[m-2], p[i]-ch[m-1]) <= 0)            m--;        ch[m++] = p[i];    }    if (n > 1)        m--;    return m;}double dis (point a, point b) {    double xx = a.x-b.x, yy = a.y-b.y;    return sqrt (xx*xx + yy*yy);}int main () {    //freopen ("in", "r", stdin);    int t, kase = 0;    scanf ("%d", &t);    while (t--) {        if (kase++)            printf ("\n");        scanf ("%d%lf", &n, &l);        for (int i = 0; i < n; i++) {            scanf ("%lf%lf", &p[i].x, &p[i].y);        }        m = ConvexHull ();        double ans = 0;        for (int i = 0; i < m; i++) {            ans += dis (ch[i], ch[(i+1)%m]);        }        ans += 2*pi*l;        printf ("%lld\n", (long long) (ans+0.5));    }    return 0;}

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