Spfa（最短路求解）

spfa（最短路求解）

模板：

#include<iostream>
#include<cstdio>
#include<queue>
#include<cstring>
using namespace std;
const int maxn = 105;
const int maxm = 100005;
struct Edge{
    int to,w,next;
}edge[maxm<<1];
int tot = 0,dis[maxn],cnt[maxn],head[maxn];  

void addedge(int u,int v,int w)
{
    edge[tot].to = v;edge[tot].w = w;edge[tot].next = head[u];
    head[u] = tot++;
}  

void spfa(int st,int ed)
{
    int i;
    queue<int>que;
    while (!que.empty())    que.pop();
    memset(dis,0x3f3f3f3f,sizeof(dis));
    memset(cnt,0,sizeof(cnt));
    que.push(st);
    dis[st] = 0;
    cnt[st] = 1;
    while (!que.empty())
    {
        int u = que.front();
        que.pop();
        if (u == ed)    continue;
        for (i = head[u];i != -1;i = edge[i].next)
        {
            int v = edge[i].to;
            if (dis[u] + edge[i].w < dis[v])
            {
                dis[v] = dis[u] + edge[i].w;
                if (!cnt[v])    que.push(v);
                cnt[v] = cnt[u];
            }
            else if (dis[u] + edge[i].w == dis[v])
            {
                if (!cnt[v])    que.push(v);
                cnt[v] += cnt[u];
            }
        }
    }
}  

int main()
{
    int N,M,S,E,u,v,w,i;
    memset(head,-1,sizeof(head));
    scanf("%d%d%d%d",&N,&M,&S,&E);
    while (M--)
    {
        scanf("%d%d%d",&u,&v,&w);
        addedge(u,v,w);
        addedge(v,u,w);
    }
    spfa(S,E);
    printf("%d %d\n",dis[E],cnt[E]);
    return 0;
}  

也可以计算有多少个最小生成树