HDU 1102Constructing Roads

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用的kruskal算法，主要就是把已经连接的路标记连接上，然后再求最小生成树就行了。

#include <cstdio>#include <algorithm>using namespace std;const int MAX = 1e4 + 5;struct EDGE{    int from, to , cost;}edge[MAX];int n, q;int fa[105], r[105];int comp(EDGE a, EDGE b){    return a.cost < b.cost;}void init(int n){    for (int i = 1; i <= n; ++i)    {        fa[i] = i;        r[i] = 1;    }}int find(int x){    return fa[x] == x ? x : fa[x] = find(fa[x]);}void unite(int a, int b){    a = find(a);    b = find(b);    if (a == b)        return ;    if (r[a] < r[b])    {        fa[a] = b;    }    else    {        fa[b] = a;        if (r[a] == r[b])            r[a]++;    }}int main(){    while (scanf("%d", &n) != EOF)    {        int cnt_e = 0;        int tmp;        init(n);        for (int i = 1; i <= n; ++i)        {            for (int j = 1; j <= n; ++j)            {                scanf("%d", &tmp);                if (i != j)                {                    ++cnt_e;                    edge[cnt_e].from = i;                    edge[cnt_e].to = j;                    edge[cnt_e].cost = tmp;                }            }        }       // printf("cnt_e = %d\n", cnt_e);        sort(edge + 1, edge + 1 + cnt_e, comp);       // printf("min_sum = %d\n", min_sum);        scanf("%d", &q);        int tmp_f, tmp_t;        for (int i = 1; i <= q; ++i)        {            scanf("%d%d", &tmp_f, &tmp_t);            //min_sum -= g[tmp_f][tmp_t];            unite(tmp_f, tmp_t);        }        int min_sum = 0;        for (int i = 1; i <= cnt_e; ++i)        {            if (find(edge[i].from) != find(edge[i].to))            {                min_sum += edge[i].cost;                unite(edge[i].from, edge[i].to);            }        }        printf("%d\n", min_sum);    }    return 0;}

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