hdu 1392 fzu 1333 Surround the Trees 简单凸包

使用凸包模版即可。

hdu 1392

/*
 * hdu1392.c
 *
 *  Created on: 2011-9-2
 *      Author: 王竹
 */

#include<stdio.h>
#include<math.h>
#include<stdlib.h>
#define nmax 1001
#define eps 1e-8
typedef struct point {
    int x, y;
} point;
point Point[nmax];
int stack[nmax];
double res;
int cross_product(point p1, point p2, point p0) {
    return (p1.x - p0.x) * (p2.y - p0.y) - (p1.y - p0.y) * (p2.x - p0.x);
}
double pDistans(point p0, point p1) {
    return sqrt((p0.x - p1.x) * (p0.x - p1.x) + (p0.y - p1.y) * (p0.y - p1.y));
}
int cmp(const void *a, const void *b) {
    point n = *(point *) a;
    point m = *(point *) b;
    double temp;
    temp = cross_product(n, m, Point[0]);
    if (temp > 0) {
        return 1;
    } else if ((fabs(temp) < eps)
            && (pDistans(m, Point[0]) >= pDistans(n, Point[0]))) {
        return 1;
    }
    return -1;
}
void solve(int n) {
    int i;
    for (i = 0, res = 0.0; i < n; i++) {
        res += pDistans(Point[stack[i]], Point[stack[(i + 1) % n]]);
    }
    printf("%.2lf\n", res);
}
void grahamScan(int n) {
    int i, k, top;
    point p;
    p = Point[0], k = 0;
    for (i = 1; i < n; i++) {
        if (p.y > Point[i].y || (p.y == Point[i].y && p.x > Point[i].x)) {
            p = Point[i], k = i;
        }
    }
    p = Point[0], Point[0] = Point[k], Point[k] = p;
    qsort(Point + 1, n - 1, sizeof(Point[0]), cmp);
    for (i = 0; i <= 2; i++) {
        stack[i] = i;
    }
    for (i = 3, top = 2; i < n; i++) {
        while (cross_product(Point[stack[top - 1]], Point[i], Point[stack[top]])
                <= 0) {
            top--;
            if (!top) {
                break;
            }
        }
        top++;
        stack[top] = i;
    }
    solve(top + 1);
}
int main() {
#ifndef ONLINE_JUDGE
    freopen("data.in", "r", stdin);
#endif
    int n, i;
    while (scanf("%d", &n) != EOF,n) {
        for (i = 0; i < n; i++) {
            scanf("%d %d", &Point[i].x, &Point[i].y);
        }
        if (n == 1) {
            puts("0.00");
            continue;
        }
        if (n == 2) {
            printf("%.2lf\n", pDistans(Point[0], Point[1]));
            continue;
        }
        grahamScan(n);
    }
    return 0;
}

fzu 1333

/*
 * hdu1392.c
 *
 *  Created on: 2011-9-2
 *      Author: 王竹
 */

#include<stdio.h>
#include<math.h>
#include<stdlib.h>
#define nmax 1001
#define eps 1e-8
typedef struct point {
    int x, y;
} point;
point Point[nmax];
int stack[nmax];
double res;
int cross_product(point p1, point p2, point p0) {
    return (p1.x - p0.x) * (p2.y - p0.y) - (p1.y - p0.y) * (p2.x - p0.x);
}
double pDistans(point p0, point p1) {
    return sqrt((p0.x - p1.x) * (p0.x - p1.x) + (p0.y - p1.y) * (p0.y - p1.y));
}
int cmp(const void *a, const void *b) {
    point n = *(point *) a;
    point m = *(point *) b;
    double temp;
    temp = cross_product(n, m, Point[0]);
    if (temp > 0) {
        return 1;
    } else if ((fabs(temp) < eps)
            && (pDistans(m, Point[0]) >= pDistans(n, Point[0]))) {
        return 1;
    }
    return -1;
}
void solve(int n) {
    int i;
    for (i = 0, res = 0.0; i < n; i++) {
        res += pDistans(Point[stack[i]], Point[stack[(i + 1) % n]]);
    }
    printf("%.2lf\n", res);
}
void grahamScan(int n) {
    int i, k, top;
    point p;
    p = Point[0], k = 0;
    for (i = 1; i < n; i++) {
        if (p.y > Point[i].y || (p.y == Point[i].y && p.x > Point[i].x)) {
            p = Point[i], k = i;
        }
    }
    p = Point[0], Point[0] = Point[k], Point[k] = p;
    qsort(Point + 1, n - 1, sizeof(Point[0]), cmp);
    for (i = 0; i <= 2; i++) {
        stack[i] = i;
    }
    for (i = 3, top = 2; i < n; i++) {
        while (cross_product(Point[stack[top - 1]], Point[i], Point[stack[top]])
                <= 0) {
            top--;
            if (!top) {
                break;
            }
        }
        top++;
        stack[top] = i;
    }
    solve(top + 1);
}
int main() {
#ifndef ONLINE_JUDGE
    freopen("data.in", "r", stdin);
#endif
    int n, i;
    while (scanf("%d", &n) != EOF,n) {
        for (i = 0; i < n; i++) {
            scanf("%d %d", &Point[i].x, &Point[i].y);
        }
        if (n == 1) {
            puts("0.00");
            continue;
        }
        if (n == 2) {
            printf("%.2lf\n", pDistans(Point[0], Point[1]) * 2.0);
            continue;
        }
        grahamScan(n);
    }
    return 0;
}