算法导论 ch22 无向图 桥

/home/a/j/nomad2:cat bridge.CPP 
#include <iostream>
using namespace std;

const int V = 7;

int bridge, edge[V][V], anc[V], pre[V], vis[V];

void dfs(int cur, int father, int dep, int n)
{
        if(bridge)
                return;

        vis[cur] = 1;
        pre[cur] = anc[cur] = dep;
        for(int i = 0; i < V; i++)
        {
                if(!edge[cur][i])
                {
                        continue;
                }

                if(i != father && 1 == vis[i])
                {
                        if (pre[i] < anc[cur])
                        {
                                anc[cur] = pre[i];
                        }
                }

                if(vis[i] == 0)
                {
                        dfs(i, cur, dep + 1, n);
                        if (bridge)
                        {
                                return;
                        }

                        if(anc[i] < anc[cur])
                        {
                                anc[cur] = anc[i];      
                        }

                        if(anc[i] > pre[cur])
                        {
                                bridge = 1;
                                cout << "found the bridge : " << cur << " -> " << i << endl;
                                return ;
                        }
                }
        }
        vis[cur] = 2;

}

void input()
{
        int v;
        for(int i = 0; i < V; i++)
        {
                for(int j = 0; j < V; j++)
                {
                        cin >> v;
                        edge[i][j] = v;
                }
        }
}

void init()
{
}

int main()
{
        input();
        dfs(0, -1, 1, V);
}

测试结果：

/home/a/j/nomad2:cat input
0 1 0 1 0 0 0
1 0 1 0 0 0 0
0 1 0 1 1 0 0
1 0 1 0 0 0 0
0 0 1 0 0 1 1
0 0 0 0 1 0 1
0 0 0 0 1 1 0
/home/a/j/nomad2:cat input|./a.out 
found the bridge : 2 -> 4