我根据算法书里面的写法改的（因为我还不会链式前向星存储图。。。。。）
#include<bits/stdc++.h>
using namespace std;
#define MAX 10000001
#define inf 0x3f3f3f
int n, m;
bool flag = true;
int edge[1001][1001], dis[MAX], sum[MAX],vis[MAX];
//sum记录负回环，vis[]记录该节点是否在队列中
void spfa(int i)
{
queue<int>a;
vis[i] = 1;
sum[i]++;
a.push(i);
while (!a.empty())
{
int i = a.front();
vis[i] = 0;
for (int j = 1; j <= n; j++)
{
if (dis[j] > dis[i] + edge[i][j])
{
dis[j] = dis[i] + edge[i][j];
if (!vis[j])
{
vis[j] = 1;
if (++sum[j] >=n)
{
flag = false;
return;
}
a.push(j);
}
}
}
a.pop();
}
}
int main()
{
cin >> n >> m;
for (int i = 1; i <= n; i++)
for (int j = 1; j <= n; j++)
edge[i][j] = inf;
for (int i = 1; i <= n; i++)
dis[i] = inf;
dis[1] = 0;
for (int i = 1; i <= m; i++)
{
int a, b, c;
cin >> a >> b >> c;
edge[a][b] = c;
}
spfa(1);
for (int i = 1; i <= n; i++)
{
if (dis[i] == inf)
{
cout << "NO" << " ";
continue;
}
cout << dis[i] << " ";
}
return 0;
}bool spfa(int u)
{
queue<int>q;
memset(vis, 0, sizeof(vis));
memset(sum, 0, sizeof(sum));
memset(dis, 0x3f, sizeof(dis));
vis[u] = 1;
dis[u] = 0;
sum[u]++;
q.push(u);
while (!q.empty())
{
int x =q.front();
q.pop();
vis[x] = 0;
for (int i = head[i]; ~i; i++)
{
int v = e[i].to;
if (dis[v] > dis[x] + e[i].w)
{
dis[v] = dis[x] + e[i].w;
if (!vis[v])
{
if (++sum[v] >= n)
return false;
vis[v] = 1;
q.push(v);
}
}
}
}
return false;
}《算法训练营》里面的写法
