图存储-前向星

int head[maxn]; 
int to[maxn*2];
int next[maxn*2];
int cnt = 0;//边的编号 
 
memset(head, -1, sizeof(head));
 
inline void add(int x,int y){
to[cnt]=y,next[cnt]=head[x],head[x]=cnt++;
to[cnt]=x,next[cnt]=head[y],head[y]=cnt++;

}
 
inline void dfs(int u)
{
   int i;
    //从节点u的第一条边开始，遍历与u相连的所有边
    for(i=head[u];i!=-1;i=next[i])  
    {  
        dfs(to[i]);
    }
}
/*
head[i]：    以ｉ为节点的边集的第一条边编号
next[i]：编号为i的边集中的下一条边编号,特定节点u的边的编号连成一个链表
to[i]：编号为i的边的终点
*/

#include <iostream>
#include <cstdio>
using namespace std;
const int maxn = 100;
const int maxm = 100000;
typedef struct edgenode {
    int to; //边的终点
    int next; //当前下一条边的编号
    int w;  //边的权值
}edgenode;
int head[maxn]; //head[i]存放已i为起点的第一条边
edgenode edge[maxm];
int edgenum = 1;
int n = 0, m = 0;
int init() {
    edgenum = 1;
    memset(head, 0, sizeof(head));//chu shi hua 0;
    return 0;
}
int outputmap(){
    for (int i = 1; i <= n; i++) {
        for (int k = head[i]; k != 0; k = edge[k].next) {
            printf("(%d --- > %d) == %d\n", i, edge[k].to, edge[k].w);
        }
    }
    return 0;
}
int main() {
    init();
    int a = 0, b = 0, c = 0;
    while (scanf("%d%d", &n, &m) == 2) {
        for (int i = 0; i < m; i++) {
            scanf("%d%d%d", &a, &b, &c);
            edge[edgenum].to = b;
            edge[edgenum].w = c;
            edge[edgenum].next = head[a];
            head[a] = edgenum;
            edgenum++;
            edge[edgenum].to = a;
            edge[edgenum].w = c;
            edge[edgenum].next = head[b];
            head[b] = edgenum;
            edgenum++;
        }
        outputmap();
        init();
    }
    return 0;
}