poj 3625 Building Roads

原题链接：http://poj.org/problem?id=3625
最小生成树。。

#include<algorithm>#include<iostream>#include<cstdlib>#include<cstring>#include<cstdio>#include<vector>#include<cmath>#include<set>using std::set;using std::sort;using std::pair;using std::swap;using std::multiset;#define pb(e) push_back(e)#define sz(c) (int)(c).size()#define mp(a, b) make_pair(a, b)#define all(c) (c).begin(), (c).end()#define iter(c) decltype((c).begin())#define cls(arr, val) memset(arr, val, sizeof(arr))#define cpresent(c, e) (find(all(c), (e)) != (c).end())#define rep(i, n) for(int i = 0; i < (int)n; i++)#define tr(c, i) for(iter(c) i = (c).begin(); i != (c).end(); ++i)const int N = 1010;const int INF = 0x3f3f3f3f;typedef unsigned long long ull;struct Node {    int x, y;    double w;    Node() {}    Node(int i, int j, double k) :x(i), y(j), w(k) {}    inline bool operator<(const Node &t) const {        return w < t.w;    }}G[(N * N) << 1];struct P {    double x, y;    inline double calc(const P &t) const {        return sqrt((x - t.x) * (x - t.x) + (y - t.y) * (y - t.y));    }}A[N];struct Kruskal {    int E, par[N], rank[N];    inline void init() {        E = 0;        rep(i, N) {            par[i] = i;            rank[i] = 0;        }    }    inline int find(int x) {        while (x != par[x]) {            x = par[x] = par[par[x]];        }        return x;    }    inline bool unite(int x, int y) {        x = find(x), y = find(y);        if (x == y) return false;        if (rank[x] < rank[y]) {            par[x] = y;        } else {            par[y] = x;            rank[x] += rank[x] == rank[y];        }        return true;    }    inline void built(int n, int m) {        int u, v;        for(int i = 1; i<= n; i++) scanf("%lf %lf", &A[i].x, &A[i].y);        for (int i = 1; i <= n; i++) {            for (int j = i + 1; j <= n; j++) {                G[E++] = Node(i, j, A[i].calc(A[j]));            }        }        while (m--) {            scanf("%d %d", &u, &v);            G[E++] = Node(u, v, 0.0);        }    }    inline double kruskal(int n) {        int tot = 0;        double ans = 0.0;        sort(G, G + E);        rep(i, E) {            Node &e = G[i];            if (unite(e.x, e.y)) {                ans += e.w;                if (++tot >= n - 1) return ans;            }        }        return -1.0;    }    inline void solve(int n, int m) {        init(), built(n, m);        printf("%.2lf\n", kruskal(n));    }}go;int main() {#ifdef LOCAL    freopen("in.txt", "r", stdin);    freopen("out.txt", "w+", stdout);#endif    int n, m;    while (~scanf("%d %d", &n, &m)) {        go.solve(n, m);    }    return 0;}