UVA 152 Tree's a Crowd

      原本以为精度问题，原来是最后需要一个换行。直接暴力是0.216，如果加个弱弱的排序优化一下是0.120。

#include <stdio.h>
#include <math.h>
#include <string.h>
#include <stdlib.h>

#define sqr(x) ((x)*(x))

typedef struct _Point {
    double x, y, z;
}Point;

int cmp(const void *_a, const void *_b) {
    Point* a = (Point *)_a;
    Point* b = (Point *)_b;

    return (int)(a->x - b->x);
}

int main() {
    Point p[5005];
    int n = 0, r[15];
    double x, y, z;

    while (scanf("%lf%lf%lf", &x, &y, &z)) {
        if (x+y+z < 1e-9)   break;
        p[n].x = x;
        p[n].y = y;
        p[n].z = z;
        n++;
    }

    qsort(p, n, sizeof (p[0]), cmp);

    memset(r, 0, sizeof (r));

    for (int i=0; i<n; i++) {
        int tmin = 10;

        for (int j=0; j<n; j++) {
            if (i == j) continue;

            if (p[j].x-p[i].x > 10) // 如果x上距离超过了10不再搜索
                break;

            int tmp = (int)(sqrt(sqr(p[i].x-p[j].x) + sqr(p[i].y-p[j].y)
                                + sqr(p[i].z-p[j].z)));
            tmin = tmin < tmp ? tmin : tmp;
        }

        r[tmin]++;
    }

    for (int i=0; i<10; i++)
        printf("%4d", r[i]);
    printf("\n");
    return 0;
}