算法笔记：邻接表

邻接表存图

图的存储一般有邻接表和邻接矩阵两种。若图是稠密的，则宜采用邻接矩阵；图是稀疏的，则应改用邻接表。因为在众多考试中 数据范围并不允许我们采用邻接矩阵 所以着重描述一下邻接表的存图方式

定义

• 边权：代表当前边上的数值

• 点权：代表当前点上的数值

• Vis数组：当前点是否被访问过

• head数组：当前起点所属的编号

• ver数组：下一条边

• to数组：上一条边的编号

这里的编号通指代码中的变量tot

学习方法

• [对于静态]知道怎么用的即可..记住存图的那个函数 和 如何遍历图 （如果实在不懂含义 是可以这么搞的）
• [对于动态]没必要去学..因为动态写的话还很容易MLE 所以看自己喜好选择了 其他的和静态的一样
  
  

扔代码

对于有边无权的情况 ``` //#define fre yes

include

include

include

include

include

using namespace std;

const int maxn = 100005;
bool Vis[maxn];
int head[maxn];
int ver[maxn];
int to[maxn];

int n,m;

templateinline void read(T&x)
{
x = 0;char c;int lenp = 1;
do { c = getchar();if(c == '-') lenp = -1; } while(!isdigit(c));
do { x = x * 10 + c - '0';c = getchar(); } while(isdigit(c));
x *= lenp;
}

void addedge(int x,int y)
{
ver[tot] = y;
to[tot] = head[x];
head[x] = tot++;
}

void kre(int x)
{
for (int i=head[x];~i;i=to[i])
{
int y = ver[i];//下一条边
if(Vis[y]) kre(y);
}
}

int main()
{
memset(head,-1,sizeof(head));

read(n);read(m);
for (int i=1;i<=m;i++)
{
    int x,y;
    read(x);read(y);
    addedge(x,y);
}
//遍历每一条边
for (int i=1;i<=n;i++) { memset(Vis,0,sizeof(Vis));kre(i); }
return 0;

}

</br>
对于有边有权的情况

//#define fre yes

include

include

include

include

include

using namespace std;

const int maxn = 100005;
bool Vis[maxn];
int head[maxn];
int edge[maxn];
int ver[maxn];
int to[maxn];

int n,m;

templateinline void read(T&x)
{
x = 0;char c;int lenp = 1;
do { c = getchar();if(c == '-') lenp = -1; } while(!isdigit(c));
do { x = x * 10 + c - '0';c = getchar(); } while(isdigit(c));
x *= lenp;
}

void addedge(int x,int y,int z)
{
ver[tot] = y;
edge[tot] = z;
to[tot] = head[x];
head[x] = tot++;
}

void kre(int x)
{
for (int i=head[x];~i;i=to[i])
{
int y = ver[i];//下一条边
if(Vis[y]) kre(y);
}
}

int main()
{
memset(head,-1,sizeof(head));

read(n);read(m);
for (int i=1;i<=m;i++)
{
    int x,y,z;
    read(x);read(y);read(z);
    addedge(x,y);
}
//遍历每一条边
for (int i=1;i<=n;i++) { memset(Vis,0,sizeof(Vis));kre(i); }
return 0;

}

</br>
手痒 还写了一份动态的（emmm..）

扔代码

//#define fre yes

include

include

include

include

include

using namespace std;

int n,m;

const int maxn = 256+10;
struct Node{
int ver;
int edge;
Node *to;
Node():to(NULL){}
};

struct VNode{
int from;
Node *Start;
VNode():Start(NULL){}
};
VNode Nmap[maxn];

templateinline void read(T&x)
{
x = 0;char c;int lenp = 1;
do { c = getchar();if(c == '-') lenp = -1; } while(!isdigit(c));
do { x = x * 10 + c - '0';c = getchar(); } while(isdigit(c));
x *= lenp;
}

void addedge(int x,int y,int z)
{
Node *now = new Node();
now->ver = y;
now->edge = z;
now->to = Nmap[x].Start;
Nmap[x].Start = now;
}

int main()
{
read(n);read(m);
for (int i=1;i<=m;i++)
{
int x,y,z;
read(x);read(y);read(z);
addedge(x,y,z);
}
for (int i=1;i<=n;i++)
{
for (Node *w = Nmap[i].Start;w!=NULL;w=w->to)
{
printf("%d %d %d\n",i,w->ver,w->edge);
}
} return 0;
}