dijkstra求最短路

//稠密图

#include
#include
#include
using namespace std;
const int N=510;
int n,m;
int g[N][N];
int dist[N];
bool st[N];
int dijkstra()
{
memset(dist,0x3f,sizeof dist);
dist[1]=0;
for(int i=0;i {
int t=-1;
for(int j=1;j<=n;j++)
if(!st[j]&&t==-1||dist[t]>dist[j])
t=j;
//if(t==n) break;(优化)
st[t]=true;
for(int j=1;j<=n;j++)
dist[j]=min(dist[j],dist[t]+g[t][j]);
}
if(dist[n]==0x3f3f3f) return -1;
return dist[n];
}
int main()
{
cin>>n>>m;
memset(g,0x3f,sizeof g);
while(m--)
{
int a,b,c;
cin>>a>>b>>c;
g[a][b]=min(g[a][b],c);
}
int t=dijkstra();
cout<
}

//稀疏图

#include
#include
#include
#include
using namespace std;
typedef pair PII;
const int N=100010;
int n,m;
int h[N],w[N],e[N],ne[N],idx;
int dist[N];
bool st[N];
void add(int a,int b,int c)
{
e[idx]=b;
w[idx]=c;
ne[idx]=h[a];
h[a]=idx++;
}
int dijkstra()
{
memset(dist,0x3f,sizeof dist);
dist[1]=0;
priority_queue,greater > heap;
heap.push({0,1});
while(heap.size())
{
auto t=heap.top();
heap.pop();
int ver=t.second,distance=t.first;
if(st[ver]) continue;
for(int i=h[ver];i!=-1;i=ne[i])
{
int j=e[i];
if(dist[j]>distance+w[i])
{
dist[j]=distance+w[i];
heap.push({dist[j],j});
}
}
}
if(dist[n]==0x3f3f3f3f) return -1;
return dist[n];
}
int main()
{
cin>>n>>m;
memset(h,-1,sizeof h);
while(m--)
{
int a,b,c;
cin>>a>>b>>c;
add(a,b,c);
}
int t=dijkstra();
cout< return 0;
}