hdu 2498 Minimal Ratio Tree

先用DFS求出全组合，然后每个组合求最小生成树。

#include<stdio.h>

#include<string.h>

#include<math.h>

#include<algorithm>

using namespace std;

int n, m, summ;

int u[10000][20];

int t[20], ff[20], nodecost[20], father[20];

int edgecost[20][20];

struct abc{ int start, end, cost; }node[20 * 20];

int find(int x)

{

    if (x != father[x]) father[x] = find(father[x]);

    return father[x];

}

void dfs(int tot, int i)

{

    int j;

    if (tot == m){ for (j = 0; j < m; j++) u[summ][j] = t[j]; summ++; return; }

    if (i > n) return;

    t[tot] = i; dfs(tot + 1, i + 1); dfs(tot, i + 1);

}

bool cmp(const abc&a, const abc&b){ return a.cost < b.cost; }

int main()

{

    int i, j, ii;

    while (~scanf("%d%d", &n, &m))

    {

        if (n == 0 && m == 0) break;

        summ = 0; dfs(0, 1);//DFS生成全组合

        for (i = 1; i <= n; i++) scanf("%d", &nodecost[i]);

        for (i = 1; i <= n; i++) for (j = 1; j <= n; j++) scanf("%d", &edgecost[i][j]);

        int sx = 0;

        for (i = 1; i <= n; i++)

        {

            for (j = i + 1; j <= n; j++)

            {

                node[sx].start = i;

                node[sx].end = j;

                node[sx].cost = edgecost[i][j];

                sx++;

            }

        }

        sort(node, node + sx, cmp);

        double minratio = 999999999;

        int edge_weight, node_weight, anss;

        for (ii = 0; ii < summ; ii++)

        {

            memset(ff, 0, sizeof(ff));

            edge_weight = 0, node_weight = 0;

            for (i = 0; i <= n; i++) father[i] = i;

            for (i = 0; i < m; i++) ff[u[ii][i]] = 1, node_weight = node_weight + nodecost[u[ii][i]];

            for (i = 0; i < sx; i++)

            {

                if (ff[node[i].start] && ff[node[i].end])

                {

                    int x = find(node[i].start);

                    int y = find(node[i].end);

                    if (x != y)

                    {

                        father[x] = y;

                        edge_weight = edge_weight + node[i].cost;

                    }

                }

            }

            if (1.0*edge_weight / node_weight < minratio) minratio = 1.0*edge_weight / node_weight, anss = ii;

        }

        for (i = 0; i < m; i++)

        {

            if (i < m - 1) printf("%d ", u[anss][i]);

            else if (i == m - 1) printf("%d\n", u[anss][i]);

        }

    }

    return 0;

}