hdu 1348 凸包模板

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http://acm.hdu.edu.cn/showproblem.php?pid=1348

造城墙问题，求出凸包加上一圈圆的周长即可

凸包模板题

#include <cstdio>#include <cstdlib>#include <cmath>#include <cstring>#include <string>#include <queue>#include <map>#include <iostream>#include <algorithm>using namespace std;#define RD(x) scanf("%d",&x)#define RD2(x,y) scanf("%d%d",&x,&y)#define RD3(x,y,z) scanf("%d%d%d",&x,&y,&z)#define clr0(x) memset(x,0,sizeof(x))#define eps 1e-9const double pi = acos(-1.0);typedef long long LL;const int modo = 1e9 + 7;const int maxn = 1e4 + 5;struct point{    int x,y;}a[maxn];int b[maxn];bool cmp(point a,point b){    return a.x < b.x || (a.x == b.x && a.y < b.y);}double dis(point a,point b){    return sqrt(double((a.x-b.x)*(a.x-b.x)) + double((a.y - b.y)*(a.y - b.y)));}int cj(point a,point b,point c){    return (a.x - c.x) * (b.y - c.y) - (a.y - c.y) *(b.x - c.x);}int m;void graham(int n){    sort(a,a+n,cmp);    b[0] = 0,b[1] = 1,b[2] = 2;    int k = 1;    for(int i = 2;i < n;++i){        while(k && cj(a[i],a[b[k]],a[b[k-1]]) >= 0)            --k;        b[++k] = i;    }    m = k;    b[++k] = n - 2;    for(int i = n - 3;i >= 0;--i){        while(k != m && cj(a[i],a[b[k]],a[b[k-1]]) >= 0)            --k;        b[++k] = i;    }    m = k;}int main() {    int n,_;double f;    RD(_);    while(_--){        RD(n);        scanf("%lf",&f);        for(int i = 0;i < n;++i){            RD2(a[i].x,a[i].y);        }        graham(n);        double ans = 0;        for(int i = 0;i < m;++i)            ans += dis(a[b[i]],a[b[i+1]]);        ans += dis(a[b[m]],a[b[0]]);        ans += pi * 2 *f;        printf("%.0lf\n",ans);        if(_>0)            puts("");    }    return 0;}

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