POJ - 3255 Roadblocks (次短路)

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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;
}

POJ - 3255 Roadblocks (次短路)

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原文地址：http://blog.csdn.net/u013167299/article/details/44995127