hdu1162 Eddy's picture 基础最小生成树

    #include <cstdio>
    #include <cmath>
    #include <cstring>
    #include <algorithm>
    #include <string>
    using namespace std;

    int n, m;
    int f[510];

    struct node
    {
        int u, v;
        double w;
    }map[10010];

    int getf(int a)
    {
        if (f[a] == a)
        {
            return a;
        }

        f[a] = getf(f[a]);
        return f[a];
    }

    void merge(int a, int b)
    {
        int x = getf(a);
        int y = getf(b);

        if (x != y)
            f[y] = x;
    }


    void init()
    {
        for (int i = 1; i <= n; i++)
            f[i] = i;
    }

    bool cmp(node a, node b)
    {
        return a.w < b.w;
    }

    double kura()
    {
        double res = 0;
        sort(map, map + m, cmp);

        for (int i = 0; i < m; i++)
        {
            if (getf(map[i].u) != getf(map[i].v))
            {
                merge(map[i].u, map[i].v);
                res += map[i].w;
            }
        }
        return res;
    }

    double a[102][2];


    int main()
    {
        while (scanf("%d", &n) != EOF)
        {
            m = n*(n - 1);
            for (int i = 1; i <= n; i++)
                scanf("%lf %lf", &a[i][0], &a[i][1]);

            int k = 0;
            for (int i = 1; i <= n; i++)
            {
                for (int j = i + 1; j <= n; j++)
                {
                    map[k].u = i;
                    map[k].v = j;
                    map[k].w = sqrt(abs(pow(a[j][0] - a[i][0], 2) + pow(a[j][1] - a[i][1], 2)));
                    k++;
                }
            }
            init();
            printf("%.2lf
", kura());
        }

        return 0;
    }