最短路模板

话不多说，放代码：

#include <bits/stdc++.h>
using namespace std;
void SPFA_scan()
{
	/*
	int n,m;
bool vis[1000005];
struct edge{
	int v,val;
};
vector<edge>dis[1000005];
int x,y,e;
int dp[1000005];
int tot[1000005];
queue<int>q;
*/
	memset(dp,0x3f,sizeof(dp));
	scanf("%d %d",&n,&m);
	for(int i=1;i<=m;i++)
	{
		scanf("%d %d %d",&x,&y,&e);
		edge now;
		now.v=y;
		now.val=e;
		dis[x].push_back(now);
		now.v=x;
		now.val=e;
		dis[y].push_back(now);
	}
}
bool SPFA(int s,int t)
{
	dp[s]=0;
	tot[s]=1;
	vis[s]=1;
	q.push(s);
	while(!q.empty())
	{
		int now=q.front();
		q.pop();
		vis[now]=0;
		for(int i=0;i<dis[now].size();i++)
		{
			int v=dis[now][i].v;
			int w=dis[now][i].val;
			if(dp[v]>dp[now]+w)
			{
				dp[v]=dp[now]+w;
				if(!vis[v])
				{
					vis[v]=1;
					tot[v]++;
					q.push(v);
					if(tot[v]>n)
					{
						return 0;
					}
				}
			}
		}
	}
	return 1;
}
void dijkstar_scan()
{
	/*
	int n,m;
	int x,y;
	bool vis[2505];
	int k;
	int e;
	int s;int t;
	int dp[2505];
	struct ss{
		int v;int val;
	};
	struct node{
		int u;
		int w;
		bool operator<(const node x)const{return w>x.w;}
	};
	vector<ss>dis[2505];
	priority_queue<node>q;
	*/ 
	memset(dp,0x3f,sizeof(dp));
	scanf("%d %d %d %d",&n,&m,&s,&t);
	for(int i=1;i<=m;i++)
	{
		scanf("%d %d %d",&x,&y,&e);
		ss now;
		now.val=e;
		now.v=y;
		dis[x].push_back(now);
		now.v=x;
		dis[y].push_back(now);
	}
}
int dijkstra(int s,int t)
{
	
	dp[s]=0;
	vis[s] = 0; 
	node now;
	now.u=s;
	now.w=0;
	q.push(now);
	while(!q.empty())
	{
		node temp=q.top();
		q.pop();
		if(vis[temp.u])
		{
			continue;
		}
		vis[temp.u]=1;
		int k=temp.u;
		for(int i=0;i<dis[k].size();i++)
		{
			int l=dis[k][i].v;
			if(dp[l]>dp[k]+dis[k][i].val)
			{
				dp[l]=dp[k]+dis[k][i].val;
				node non;
				non.u=l;
				non.w=dp[l];
				q.push(non);
				
			}
		}
	}
	return dp[t];
}
void print_dijkstra()
{
	printf("%d",dijkstra(s,t));
}

void floyd_scan()
{
/*int n, m, ty;
int x, y;
int e;
int dis[505][505];
int pre[505][505];
int s, t;*/ 
	memset(dis,0x3f,sizeof(dis));
	scanf("%d %d",&n,&m);
	for (int i = 1; i <= m; i++) {
        scanf("%d %d %d", &x, &y, &e);
        dis[x][y] = e;
        dis[y][x] = e;
    }
	
	for(int i=1;i<=n;i++)
	{
		for(int j=1;j<=n;j++)
		{
			if(i==j)
			{
				pre[i][j]=0;
			}
			else
			{
				pre[i][j]=i;
			}
		}
		dis[i][i]=0;
	}
}
void print_floyd(int x)
{
	if(pre[s][x]==0)
	{
		return;
	}
	print(pre[s][x]);
	printf(" %d",x);
}
void floyd()
{
	
	for (int k = 1; k <= n; k++) {
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= n; j++) {
                if (dis[i][j] > dis[i][k] + dis[k][j]) {
                    dis[i][j] = dis[i][k] + dis[k][j];
                }
            }
        }
    }
}
int main()
{
	
}