USACO 2006 November Gold
//#include<bits/stdc++.h>
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<string>
#include<queue>
#include<vector>
#include<map>
#include<cstdlib>
#include<set>
#include<stack>
#include<cstring>
using namespace std;
template<class T>inline T read(T&x)
{
char c;
while((c=getchar())<=32)if(c==EOF)return -1;
bool ok=false;
if(c=='-')ok=true,c=getchar();
for(x=0; c>32; c=getchar())
x=x*10+c-'0';
if(ok)x=-x;
return 1;
}
template<class T> inline T read_(T&x,T&y)
{
return read(x)!=-1&&read(y)!=-1;
}
template<class T> inline T read__(T&x,T&y,T&z)
{
return read(x)!=-1&&read(y)!=-1&&read(z)!=-1;
}
template<class T> inline void write(T x)
{
if(x<0)putchar('-'),x=-x;
if(x<10)putchar(x+'0');
else write(x/10),putchar(x%10+'0');
}
template<class T>inline void writeln(T x)
{
write(x);
putchar('\n');
}
//-------ZCC IO template------
const int maxn=1000001;
const double inf=999999999;
#define lson (rt<<1),L,M
#define rson (rt<<1|1),M+1,R
#define M ((L+R)>>1)
#define For(i,t,n) for(int i=(t);i<(n);i++)
typedef long long LL;
typedef double DB;
typedef pair<int,int> P;
#define bug printf("---\n");
#define mod 10007
int V,E;
struct edge
{
int to,cost;
edge(int a,int b){to=a;cost=b;}
};
vector<edge> G[maxn];
int d[maxn];
int d1[maxn];
void solve(int s)
{
priority_queue<P,vector<P>,greater<P> > q;
For(i,0,V+1)
{
d[i]=d1[i]=inf;
}
q.push(P(0,s));
while(!q.empty())
{
P tmp=q.top();q.pop();
int v=tmp.second;int dis=tmp.first;
if(d1[v]<dis)continue;
int N=G[v].size();
for(int i=0;i<N;i++)
{
edge e=G[v][i];
int d2=dis+e.cost;
if(d[e.to]>d2)
{
swap(d[e.to],d2);
//d[e.to]=d2;
q.push(P(d[e.to],e.to));
}
if(d1[e.to]>d2&&d2>d[e.to])
{
d1[e.to]=d2;
q.push(P(d1[e.to],e.to));
}
}
}
writeln(d1[V]);
}
int main()
{
//#ifndef ONLINE_JUDGE
//freopen("in.txt","r",stdin);
// #endif // ONLINE_JUDGE
int n,m,i,j,k,t;
while(read_(V,E))
{
for(int i=0;i<E;i++)
{
int a,b,c;
read__(a,b,c);
G[a].push_back(edge(b,c));
G[b].push_back(edge(a,c));
}
solve(1);
For(i,0,V)G[i].clear();
}
return 0;
}
原文：http://blog.csdn.net/u013167299/article/details/44995127