蓝桥杯 算法训练 最短路 spfa

参考自：http://www.cnblogs.com/scau20110726/archive/2012/11/18/2776124.html

分成bfs与dfs两种思路

方法一：bfs

#include <iostream>#include <cstring>#include <queue>#include <cmath>using namespace std;  #define MAX_N 20010#define MAX_M 200010   #define MAX 200000010int head[MAX_N]; bool vis[MAX_N];   int dis[MAX_N]; int n,m; struct node{int v,value; int next; }edge[MAX_M];  int cur=0; void add(int u,int v,int val){node E={v,val,head[u]}; edge[cur]=E;head[u]=cur++; }void spfa(int x){ for (int i=1;i<=n;i++){dis[i]=MAX; vis[i]=0; }queue<int>q;     q.push(x); vis[x]=1; dis[x]=0; while(!q.empty()){int u=q.front(); q.pop();vis[x]=0; for(int i=head[u];i!=-1;i=edge[i].next){node E=edge[i]; if (dis[E.v]>dis[u]+E.value)  {dis[E.v]=dis[u]+E.value;  if (!vis[E.v]){vis[E.v]=1; q.push(E.v);   }}}}} int main(){ memset(head,-1,sizeof(head));  cin>>n>>m; int u,v,val;  for (int i=1;i<=m;i++){cin>>u>>v>>val;    add(u,v,val); } spfa(1); for(int i=2;i<=n;i++){cout<<dis[i]<<endl; }return 0;}

方法二:dfs 

#include <iostream>#include <cstring>using namespace std;  #define MAX_N 20010#define MAX_M 200010   #define MAX 200000010int head[MAX_N];  int dis[MAX_N]; struct node{int v,value; int next; }edge[MAX_M];  int cur=0; void add(int u,int v,int val){node E={v,val,head[u]}; edge[cur]=E;head[u]=cur++; }void spfa_dfs(int u){for(int k=head[u]; k!=-1; k=edge[k].next){int v=edge[k].v,w=edge[k].value;  if( dis[u]+w < dis[v] ){  dis[v]=dis[u]+w;spfa_dfs(v); }}} int main(){ memset(head,-1,sizeof(head));   int n,m;  cin>>n>>m; for (int i=1;i<=n;i++){dis[i]=MAX; }dis[1]=0; int u,v,val;  for (int i=1;i<=m;i++) {cin>>u>>v>>val;    add(u,v,val); } spfa_dfs(1); for(int i=2;i<=n;i++){cout<<dis[i]<<endl; }return 0;}