我是大学生，这是我第一次在这里提问。首先感谢您花时间阅读。我们有一个关于Graphs的项目。到目前为止，我通过矩阵和邻接列表创建了图形。我的邻接列表版本由2个链表组成（只是为了允许添加我想要的顶点）。 现在我正在尝试进行深度优先搜索。我做了一些研究而且认真对待我并不太了解，所以我按照自己的想法。它正在工作，但我不确定它是否正确或复杂性是否为O（V + E）v指的是顶点和E边缘..任何人都可以阅读它并告诉我它是否正确？如果是复杂度O（V + E）怎么样？ PS：请只使用c ++，因为它是我所知道的唯一语言。 非常感谢你的帮助
我在DFS中所做的是
1-do while循环遍历所有顶点并在每个顶点上调用DFS
在每个顶点上，调用DFS，顶点的颜色为灰色（'g'）
3-another while循环遍历目标顶点的子节点（边缘）
4对每个孩子，另一个while循环将通过search-＆gt;搜索相应的边缘。 value == child-＆gt; value
5 - 当它找到顶点时，它将再次调用DFS（所以重复步骤2到5）
6-完成后，颜色顶点黑色一个接一个
以下是代码：
EdgeNode.h
class EdgeNode
{
public:
int value;
EdgeNode *Next;
};
VertexNode.h
#include "EdgeNode.h"
class VertexNode
{
public:
int value;
int parentIndex;
char color;
EdgeNode *Child;
VertexNode *Next;
};
Graph.h
#include "VertexNode.h"
class Graph{
public:
int NbVertex;
int time;
VertexNode *s;
Graph();
void AddVertex(int value);
bool AddEdge(int parentIndex, int value);
void PrintVertex();
void PrintGraph();
void DepthFirstSearch();
void DFS(VertexNode *V);
};
Graph.cpp
#include <iostream>
#include "Graph.h"
#include <string>
using namespace std;
Graph::Graph()
{
s = NULL;
NbVertex = 0;
}
void Graph::AddVertex(int value)
{
if (NbVertex == 0)
{
s = new VertexNode;
s->value = value;
s->parentIndex = NbVertex+1;
s->color = 'w';
s->Child = NULL;
s->Next = NULL;
}
else
{
VertexNode *z = s;
while (z->Next != NULL)
{
z = z->Next;
}
z->Next = new VertexNode;
z->Next->parentIndex = NbVertex+1;
z->Next->color = 'w';
z->Next->value = value;
z->Next->Child = NULL;
z->Next->Next = NULL;
}
NbVertex++;
}
bool Graph::AddEdge(int parentIndex, int value)
{
if (NbVertex == 0)
cout << "Graph is empty" << endl;
VertexNode *z = s;
while (z != NULL)
{
if (z->parentIndex == parentIndex)
{
if (z->Child == NULL)
{
EdgeNode *y = new EdgeNode;
y->value = value;
y->Next = NULL;
z->Child = y;
}
else
{
EdgeNode *y = z->Child;
while (y->Next != NULL)
{
if (y->value == value)
{
cout << "The edge already exists"<<endl;
return false;
}
y = y->Next;
}
y->Next = new EdgeNode;
y->Next->value = value;
y->Next->Next = NULL;
}
return true;
}
z = z->Next;
}
cout << "The index was not found" << endl;
return false;
}
void Graph :: PrintVertex()
{
VertexNode *z = s;
int count = 1;
while (z != NULL)
{
cout << "vertex " << count << " : " << endl;
cout << "Value : " << z->value << endl;
cout << "Index : " << z->parentIndex << endl;
cout << "Next : " << z->Next << endl;
cout << "Child : " << z->Child << endl;
cout << "Color : " << z->color << endl;
cout << endl;
count++;
z = z->Next;
}
cout << "time is : " << time;
}
void Graph::PrintGraph()
{
VertexNode *z = s;
int countVertex = 1;
while (z != NULL)
{
cout << "vertex " << countVertex << " : " << endl;
cout << "Value : " << z->value << endl;
cout << "Index : " << z->parentIndex << endl;
cout << "Next : " << z->Next << endl;
cout << "Child : " << z->Child << endl;
cout << endl;
countVertex++;
if (z->Child != NULL)
{
int countChild=1;
EdgeNode *y = z->Child;
while (y != NULL)
{
cout << "Child " << countChild << " : " << endl;
cout << "Value : " << y->value << endl;
cout <<"Next : " << y->Next << endl;
cout << "-------------------"<<endl;
countChild++;
y = y->Next;
}
}
cout << "*************************************"<<endl;
z = z->Next;
}
}
void Graph :: DepthFirstSearch()
{
time = 0;
VertexNode *z = s;
while (z != NULL)
{
if (z->color == 'w')
{
DFS(z);
}
z = z->Next;
}
}
void Graph::DFS(VertexNode *V)
{
cout << "(" << V->value;
V->color = 'g';
time++;
EdgeNode *Y = V->Child;
while (Y != NULL)
{
VertexNode *Search = s;
while (Search != NULL)
{
if (Search->value == Y->value)
{
if (Search->color == 'w')
{
DFS(Search);
}
/*else
{
Search->color = 'b';
}*/
}
Search = Search->Next;
}
Y = Y->Next;
}
V->color = 'b';
time++;
cout << V->value << ")";
}
这是DFS
void Graph :: DepthFirstSearch()
{
time = 0;
VertexNode *z = s;
while (z != NULL)
{
if (z->color == 'w')
{
DFS(z);
}
z = z->Next;
}
}
void Graph::DFS(VertexNode *V)
{
cout << "(" << V->value;
V->color = 'g';
time++;
EdgeNode *Y = V->Child;
while (Y != NULL)
{
VertexNode *Search = s;
while (Search != NULL)
{
if (Search->value == Y->value)
{
if (Search->color == 'w')
{
DFS(Search);
}
/*else
{
Search->color = 'b';
}*/
}
Search = Search->Next;
}
Y = Y->Next;
}
V->color = 'b';
time++;
cout << V->value << ")";
}
答案 0 :(得分：0)
我不知道您的项目应该如何有条理，但使用邻接列表构建的图表的代码大约需要10行。
快速查看它，你的DFS似乎是正确的。从理论上讲，DFS（BFS）时间是O（V + E），因为它将通过所有顶点和所有边缘（总计O（| V | + | E |）。
如果您关心代码阅读和组织，请继续，但如果您更喜欢代码，我相信您可以找到更小的图形实现。
DFS的5行实现工作正常。
void DFS(graph G, int v){
mark[v] = true;
cout<<"Visiting "<<v<<endl;
for(auto u : G[v]) //this means "for all u in the adjacence list of v"
if(!mark[u]) DFS(G, u);
}