1     const int INF = 9999999999;//设一个较大的数为无穷大
 2     int n, m;//n为点数，m为边数
 3     int e[5005][5005];//貌似开5005*5005就快MLE了...所以要谨慎一点
 4     for (int i = 1; i <= n; i++)
 5         for (int j = 1; j <= n; j++)
 6             if (i == j)
 7                 e[i][j] = 0;//我自己到我自己的距离当然是0
 8             else
 9                 e[i][j] = INF;//一开始还没有边，所以我到其他人的距离先设为无穷大
10     for (int i = 1; i <= m; i++)//读入边
11     {
12         int from, to, weight;//从哪来，到哪去，路多长
13         cin >> from >> to >> weight;
14         e[from][to] = weight;//无向图存两遍
15         e[to][from] = weight;//from到to的距离和to到from的距离是相等的
16     }

 1 #include<iostream>
 2 using namespace std;
 3 struct edge
 4 {
 5     int from;
 6     int to;
 7     int next;//模拟指针
 8     int weight;
 9 }e[2000080];//看吧，他开很大都不会爆，不过要注意无向图开两倍
10 //毕竟一条无向边其实是当作两条有向边存的
11 int head[50005];//head[i]表示点i所发出的第一条边的数组下标
12 int tot;//边的总数
13 int n, m;
14 void add(int from,int to,int weight)
15 {
16     tot++;
17     e[tot].from = from;
18     e[tot].to = to;
19     e[tot].weight = weight;
20     e[tot].next = head[from];
21     head[from] = tot;
22 }//加边的模板
23 int main()
24 {
25     cin >> n >> m;
26     for (int i = 1; i <= m; i++)
27     {
28         int x, y, z;
29         cin >> x >> y >> z;
30         add(x, y, z);
31         add(y, x, z);//依然无向边存两次
32     }
33     for (int i = head[1]; i; i = e[i].next)
34         //遍历该点上所有的边，如果没有下一条了（i=0），我就停
35         //如果还有下一条边，我就继续往后遍历（i=e[i].next）
36         cout << e[i].to;
37     //貌似没解释清楚，感性理解一下？
38     return 0;
39 }

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
struct edge
{
    int from;
    int to;
    int weight;
};
vector<edge> e[100086];//e[i][j]表示点i的第j条边
//貌似比邻接表稍微简单一点
int n, m;
int main()
{
    cin >> n >> m;
    for (int i = 1; i <= n; i++)
    {
        edge t;//定义一条新的的边出来
        int x, y, z;
        cin >> x >> y >> z;
        t.from = x;
        t.to = y;
        t.weight;
        e[x].push_back(t);//把他塞进去
        t.from = y;
        t.to = x;
        e[y].push_back(t);//改一改，反向塞进去
    }
    for (int i = 0; i < e[1].size(); i++)
        //查询很方便
        //不过注意vector是从0开始的
        cout << e[1][i].to;
    return 0;
}

1     for (int k = 1; k <= n; k++)//枚举中间点
2         for (int i = 1; i <= n; i++)//枚举起点
3             for (int j = 1; j <= n; j++)//枚举终点
4                 e[i][j] = min(e[i][j], e[i][k] + e[k][j]);//替换

 1 #include<iostream>
 2 #include<vector>
 3 #include<algorithm>
 4 using namespace std;
 5 int e[1000][1000];
 6 int main()
 7 {
 8     int n, m;
 9     cin >> n >> m;
10     for (int i = 1; i <= n; i++)
11         for (int j = 1; j <= m; j++)
12             if (i == j)
13                 e[i][j] = 0;
14             else
15                 e[i][j] = 9999999;
16     for (int i = 1; i <= m; i++)
17     {
18         int x, y, z;
19         cin >> x >> y >> z;
20         e[x][y] = z;
21         e[y][z] = z;
22     }
23     for (int k = 1; k <= n; k++)//枚举中间点
24         for (int i = 1; i <= n; i++)//枚举起点
25             for (int j = 1; j <= n; j++)//枚举终点
26                 e[i][j] = min(e[i][j], e[i][k] + e[k][j]);//替换
27     return 0;
28 }

 1 #include<iostream>
 2 #include<algorithm>
 3 using namespace std;
 4 const long inf = 20041001;
 5 int n;
 6 int m;
 7 int s;
 8 int tot;
 9 struct edge
10 {
11     long weight;
12     int to;
13     int next;
14 }e[500005];
15 struct node
16 {
17     int head;
18 }no[10086];
19 long long dis[10086];
20 bool book[10086];
21 void add(int from, int to, int weight)
22 {
23     tot++;
24     e[tot].to = to;
25     e[tot].weight = weight;
26     e[tot].next = no[from].head;
27     no[from].head = tot;
28 }
29 int main()
30 {
31     cin >> n >> m >> s;
32     book[s] = 1;
33     for (int i = 1; i <= n; i++)
34         dis[i] = inf;
35     dis[s] = 0;
36     for (int i = 1; i <= m; i++)
37     {
38         int x, y, w;
39         cin >> x >> y >> w;
40         if (x != y)
41             add(x, y, w);
42     }
43     for (int i = no[s].head; i; i = e[i].next)
44     {
45         if (e[i].weight < dis[e[i].to])
46             dis[e[i].to] = e[i].weight;
47     }
48     for (int i = 1; i < n; i++)
49     {
50         int u = 0;
51         int minn = inf;
52         for (int j = 1; j <= n; j++)
53         {
54             if (book[j] == 0 && dis[j] < minn)
55             {
56                 minn = dis[j];
57                 u = j;
58             }
59         }
60         book[u] = 1;
61         for (int i = no[u].head; i; i = e[i].next)
62         {
63             if (dis[e[i].to] > dis[u] + e[i].weight)
64                 dis[e[i].to] = dis[u] + e[i].weight;
65         }
66     }
67     for (int i = 1; i <= n; i++)
68         cout << dis[i] << " ";
69     return 0;
70 }

 1 #include<iostream>
 2 #include<string.h>
 3 #include<algorithm>
 4 #include<vector>
 5 #include<map>
 6 #include<bitset>
 7 #include<set>
 8 #include<string>
 9 #if !defined(_WIN32)
10 #include<bits/stdc++.h>
11 #endif // !defined(_WIN32)
12 #define ll long long
13 #define dd double
14 using namespace std;
15 int t;
16 int n, m, w;
17 int tot;
18 struct edge
19 {
20     int from;
21     int to;
22     int weight;
23 }e[100086];
24 int dis[5005];
25 void add(int x, int y, int z)
26 {
27     tot++;
28     e[tot].from = x;
29     e[tot].to = y;
30     e[tot].weight = z;
31 }
32 bool Bellman_Ford()
33 {
34     memset(dis, 0x3f3f3f3f, sizeof(dis));
35     dis[1] = 0;
36     for (int i = 1; i < n; i++)
37     {
38         for (int j = 1; j <= tot; j++)
39         {
40             if (dis[e[j].to] > dis[e[j].from] + e[j].weight)
41                 dis[e[j].to] = dis[e[j].from] + e[j].weight;
42         }
43     }
44     for (int i = 1; i <= tot; i++)
45         if (dis[e[i].to] > dis[e[i].from] + e[i].weight)
46             return 0;
47     return 1;
48 }
49 int main()
50 {
51     cin >> t;
52     while (t--)
53     {
54         tot = 0;
55         memset(e, 0, sizeof(e));
56         memset(dis, 0, sizeof(dis));
57         n = 0, m = 0, w = 0;
58         cin >> n >> m >> w;
59         for (int i = 1; i <= m; i++)
60         {
61             int x, y, z;
62             cin >> x >> y >> z;
63             add(x, y, z);
64             add(y, x, z);
65         }
66         for (int i = 1; i <= w; i++)
67         {
68             int x, y, z;
69             cin >> x >> y >> z;
70             add(x, y, 0 - z);
71         }
72         if (Bellman_Ford())
73             cout << "NO" << endl;
74         else
75             cout << "YES" << endl;
76     }
77     return 0;
78 }