SPFA 最短路径打印方法

#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <queue>
#include <cmath>
#include <cstring>
using namespace std;
#define INF 0xfffffff
#define maxn 40
 
struct Edge
{
    int e, w;
    Edge(int e=,int w=) : e(e), w(w) {}
};
int Path[maxn], n, dist[maxn];
bool vis[maxn];
vector<Edge> G[maxn];
 
void Spfa(int Star,int End)
{
    Edge P, Pn;
    dist[Star] = ;
    queue<Edge> Q;
    Q.push(Edge(Star,));
 
    while( !Q.empty() )
    {
        P = Q.front();
        Q.pop();
        vis[P.e] = true;
 
        int len = G[P.e].size();
 
        for(int i=; i<len; i++)
        {
            Pn = G[P.e][i];
 
            if(dist[Pn.e] > dist[P.e] + Pn.w)
            {
                dist[Pn.e] = dist[P.e] + Pn.w;
                Path[Pn.e] = P.e;
                if( !vis[Pn.e] )
                {
                    Q.push(Pn);
                    vis[Pn.e] = true;
                }
            }
        }
    }
}
 
void PutPath(int Star,int End)
{
    if(Star == End)
    {
        printf("%d", Star);
        return ;
    }
 
    PutPath(Star, Path[End]);
 
    printf("---->%d", End);
}
void Init()
{
    for(int i=; i<=n; i++)
    {
        G[i].clear();
        dist[i] = INF;
        vis[i] = false;
        Path[i] = i;
    }
}
 
int main()
{
    int m;
    cin >> n >> m;
 
    Init();
 
    for(int i=; i<=m; i++)
    {
        int a, b, c;
        cin >> a >> b >> c;
        G[a].push_back(Edge(b,c));
    }
 
    Spfa(, n);
 
    printf("%d\n", dist[n]);
 
    PutPath(,n);
 
    return ;
}
/*
4 3
1 2 1
2 3 1
3 4 1
*/