Zhejiang University Edition "Data Structure (2nd Edition)" topic collection-example 6.1

Example 6.1 Six-dimensional space (30point(s))

The "Six Degrees of Separation" theory is also called the "Six Degrees of Separation" theory. This theory can be easily stated as: "There are no more than six people between you and any stranger. That is to say, you can know any stranger through at most five people." As shown in Figure 1. .

Example:

#include <iostream>
#include <iomanip>
#include <vector>
#include <deque>

using namespace std;

#define MaxVertexNum  1008
typedef int WeightType;
typedef int Vertex;
typedef struct GNode *PtrToGNode;
struct GNode {
    int Nv;
    int Ne;
    WeightType G[MaxVertexNum][MaxVertexNum];
};
typedef PtrToGNode Graph;

Graph ReadG()
{
    Graph G = new GNode;
    cin >> G->Nv >> G->Ne;
    for(int i = 0; i < G->Ne; i++) {
        int s, d;
        cin >> s >> d;
        G->G[s][d] = 1;
        G->G[d][s] = 1;
    }
    return G;
}

deque<Vertex> queue(MaxVertexNum);

double SixDegree(Graph G, Vertex i)
{
    vector<bool> Visited(G->Nv);
    vector<int>  Dist(G->Nv);
    Visited[i] = true;
    Dist[i] = 0;
    queue.push_back(i);
    while(!queue.empty()) {
        i = queue.front();
        queue.pop_front();
        for(Vertex k = 1; k <= G->Nv; k++) {
            if(G->G[i][k] && !Visited[k]) {
                Visited[k] = true;
                Dist[k] = Dist[i]+1;
                if(Dist[k] < 6) queue.push_back(k);
            }
        }
    }
    int cnt = 0;
    for(Vertex k = 1; k <= G->Nv; k++) {
        if(Visited[k]) cnt++;
    }
    return (double)cnt/G->Nv * 100;
}

int main()
{
    Graph G = ReadG();
    for(Vertex i = 1; i <= G->Nv; i++) {
        cout << i << ": " << scientific << fixed << setprecision(2) << SixDegree(G, i) << '%' << endl;
    }
    return 0;
}

Ideas:

The BFS of the undirected graph uses Dist to record the distance. When the distance is equal to 6, there is no need to join the team. Finally, the number in Visited is the vertex that meets the requirements.