最小生成树

class Kruskal {
#define Kruskal_MAXN 100
#define Kruskal_MAXM 10005
public:
    Union_Find_Set ufs;
    int x[Kruskal_MAXM], y[Kruskal_MAXM], w[Kruskal_MAXM], N, M;
    Kruskal() {
        N = 0;
        M = 0;
    }
    void clear() {
        N = 0;
        M = 0;
    }
    void addEdge(int a, int b, int c) {
        x[M] = a;
        y[M] = b;
        w[M] = c;
        M++;
        x[M] = b;
        y[M] = a;
        w[M] = c;
        M++;
    }
    void sort(int l, int r) {
        int i = l, j = r, m = w[(l + r) >> 1], t;
        do {
            while (w[i] < m) {
                i++;
            }
            while (m < w[j]) {
                j--;
            }
            if (i <= j) {
                t = x[i];
                x[i] = x[j];
                x[j] = t;
                t = y[i];
                y[i] = y[j];
                y[j] = t;
                t = w[i];
                w[i] = w[j];
                w[j] = t;
                i++;
                j--;
            }
        } while (i <= j);
        if (l < j) {
            sort(l, j);
        }
        if (i < r) {
            sort(i, r);
        }
    }
    int MST() {
        sort(0, M - 1);
        ufs.clear(N + 1);
        int cnt = 0, ret = 0;
        for (int i = 0; i < M; i++) {
            if (cnt == N - 1) {
                return ret;
            }
            if (ufs.getFather(x[i]) != ufs.getFather(y[i])) {
                ufs.merge(x[i], y[i]);
                ret += w[i];
                cnt++;
            }
        }
        if (cnt == N - 1) {
            return ret;
        } else {
            return -1;
        }
    }
};