HDU 3367

贪心+并查集~~~

#include <cmath>#include <cstdio>#include <cstdlib>#include <cstring>#include <iostream>#include <algorithm>#define  inf 0x3f3f3f3f#define  INF 0x3f3f3f3f3f3f3f3fLLusing namespace std;const int MAXN = 10010;const int MAXM = 100010;struct Edge{    int u, v, w;    Edge() {}    Edge(int t_u, int t_v, int t_w) : u(t_u), v(t_v), w(t_w) {}    bool operator < (const Edge &e) const    {        return w < e.w;    }}edge[MAXM];int parent[MAXN], rank[MAXN], ncycle[MAXN];void init_set(){    memset(parent, -1, sizeof(parent));    memset(rank, 0, sizeof(rank));    memset(ncycle, 0, sizeof(ncycle));}int find_set(int u){    return parent[u] < 0 ? u : parent[u] = find_set(parent[u]);}void union_set(int r1, int r2, int w){    if(parent[r2] < parent[r1])    {        parent[r2] += parent[r1];        parent[r1] = r2;        rank[r2] += rank[r1];        rank[r2] += w;        ncycle[r2] += ncycle[r1];    }    else    {        parent[r1] += parent[r2];        parent[r2] = r1;        rank[r1] += rank[r2];        rank[r1] += w;        ncycle[r1] += ncycle[r2];    }}int main(){    //freopen("aa.in", "r", stdin);    int n, m, r1, r2;    while(scanf("%d %d", &n, &m) && n+m)    {        for(int i = 1; i <= m; ++i)        {            scanf("%d %d %d", &edge[i].u, &edge[i].v, &edge[i].w);        }        sort(edge + 1, edge + m + 1);        init_set();        for(int i = m; i >= 1; --i)        {            r1 = find_set(edge[i].u);            r2 = find_set(edge[i].v);            if(r1 != r2 && ncycle[r1] + ncycle[r2] <= 1)            {                union_set(r1, r2, edge[i].w);            }            else            {                if(ncycle[r1] == 0)                    rank[r1] += edge[i].w, ncycle[r1]++;            }        }        int ans = 0;        for(int i = 0; i < n; ++i)        {            if(parent[i] < 0)                ans += rank[i];        }        printf("%d\n", ans);    }    return 0;}