SPFA模板

建图：

 

const int SIZE = 100010;
const int INF = 0x3f3f3f3f;
int u[4*SIZE], w[4*SIZE], v[4*SIZE], next[4*SIZE];   //一般是4*SIZE
int first[SIZE], d[SIZE];
int sum[SIZE];
int n, m;    //n个顶点，m条边。 

memset(first, -1, sizeof(first));

void read_graph(int u1, int v1, int w1)
{
    for(int e = 0; e < n; e++)
    {
        scanf("%d%d%d", &u[e], &v[e], &w[e]);
        next[e] = first[u[e]];
        first[u[e]] = e;
    }
}

 

队列：

 

int spfa(int src)
{
    queue<int> q;
    bool inq[SIZE] = {0};
    for(int i = 0; i <= n; i++) d[i] = (i == src)? 0:INF;
    q.push(src);
    while(!q.empty())
    {
        int x = q.front(); q.pop();
        inq[x] = 0;
        for(int e = first[x]; e!=-1; e = next[e]) if(d[v[e]] > d[x]+w[e])
        {
            d[v[e]] = d[x]+w[e];
            if(!inq[v[e]])
            {
                inq[v[e]] = 1;
                if(++sum[v[e]] > n)   //判断负环 
                {
                    return -1;
                }
                q.push(v[e]);
            }
        }
    }
    if(d[n] == INF) return -2;
    else return d[n];
}

 

 

堆栈：

 

int spfa(int src)
{
    int stack[SIZE] = {0};
    bool ins[SIZE] = {0};
    int top = 0;
    for(int i = 1; i <= n; i++) d[i] = (i == src)? 0:INF;
    stack[top++] = src;
    while(top)
    {
        int x = stack[--top];
        ins[x] = 0;
        for(int e = first[x]; e!=-1; e = next[e]) if(d[v[e]] > d[x] + w[e])
        {
            d[v[e]] = d[x]+w[e];
            if(!ins[v[e]])
            {
                ins[v[e]] = 1;
                if(++sum[v[e]] > n)
                {
                    return -1;
                }
                stack[top++] = v[e];
            }
        }
    }
    if(d[n] == INF) return -2;
        return d[n];
}//SPFA的堆栈实现