基本思想:
首先訪問初始點v,之後依次訪問v的各個未成訪問過的鄰接點,然後分別從這些鄰接點出發依次訪問他們的鄰接點,直至圖中所有已被訪問的頂點的鄰接點都被訪問到。
圖的廣度優先遍歷類似於樹的按層次遍歷的過程,要用到數據結構隊列,下面直接給出實現代碼。
#include <cstdlib>
#include <iostream>
#include <queue>
#include "graph.h"
template<class T>
void BFS(const Graph<T>& g, int v, vector<bool>& visit)
{
queue<int> q;
cout<<g.getVertexName(v)<<" ";
visit[v] = true;
q.push(v);
int w;
while(!q.empty())
{
v = q.front();
q.pop();
w = g.getFirstNeighbor(v);
while(w != -1)
{
if(!visit[w])
{
cout<<g.getVertexName(w)<<" ";
visit[w] = true;
q.push(w);
}
w = g.getNextNeighbor(v,w);
}
}
}
template<class T>
void breadthFirstSearch(const Graph<T>& g, vector<bool>& visit)
{
int n = g.getNumberOfVertex();
for(int v=0; v<n; v++)
{
if(!visit[v])
BFS(g,v,visit);
}
}
int main(int argc, char *argv[])
{
Graph<char> graph("graph3.dat");
cout<<"after read the graph :"<<endl;
graph.printGraph();
int n = graph.getNumberOfVertex();
vector<bool> visit(n,false);
cout<<"BFS: ";
breadthFirstSearch(graph,visit);
cout<<endl<<endl;
system("PAUSE");
return EXIT_SUCCESS;
}
作爲單個函數實現如下:
template<class T>
void breadthFirstSearch(const Graph<T>& g, vector<bool>& visit)
{
int n = g.getNumberOfVertex();
queue<int> q;
int w;
for(int v=0; v<n; v++)
{
if(!visit[v])//頂點v未被訪問
{
visit[v] = true;
cout<<g.getVertexName(v)<<" ";//訪問頂點v
q.push(v);
while(!q.empty())//隊列非空
{
v = q.front();
q.pop();
w = g.getFirstNeighbor(v);
while(w != -1)
{
cout<<g.getVertexName(w)<<" ";
visit[w] = true;
q.push(w);
w = g.getNextNeighbor(v,w);
}
}
}
}
}
參考資料:
[1]《數據結構》劉大有 唐海鷹等著 高等教育出版社
[2][嚴蔚敏《數據結構(C語言版)》