10034.cpp

#include <algorithm>
#include <cfloat>
#include <cmath>
#include <cstdio>
#include <cstring>

using namespace std;

struct Node {
    double x, y;
};

int main(void)
{
    int    i, j, k, times, len, done, minIndex;
    Node   list[101], tmpN;
    double sum, min, tmpD;

    scanf("%d", &times);

    while (times-- > 0) {
        scanf("%d", &len);
        for (i = 0; i < len; ++i)
            scanf("%lf %lf", &list[i].x, &list[i].y);

        sum  = 0;
        done = 1;
        for (i = 1; i < len; ++i) {
            min = DBL_MAX;
            for (j = 0; j < done; ++j)
                for (k = done; k < len; ++k) {
                    tmpD = pow(list[j].x - list[k].x, 2) + pow(list[j].y - list[k].y, 2);
                    if (tmpD < min) {
                        min      = tmpD;
                        minIndex = k;
                    }
                }
            sum += sqrt(min);
            memcpy(&tmpN, list + done, sizeof(Node));
            memcpy(list + done, list + minIndex, sizeof(Node));
            memcpy(list + minIndex, &tmpN, sizeof(Node));
            done++;
        }

        printf("%.2lf\n", sum);
        if (times > 0) printf("\n");
    }

    return 0;
}