地铁 Dijkstra(优先队列优化) 湖南省第五届省赛

Posted 2020-08-08 youmi

传送门：地铁

思路：拆点，最短路；拆点比较复杂，所以对边进行最短路，spfa会tle，所以改用Dijkstra(优先队列优化)  

模板

/**************************************************************
    Problem:
    User: youmi
    Language: C++
    Result: Accepted
    Time:
    Memory:
****************************************************************/
//#pragma comment(linker, "/STACK:1024000000,1024000000")
//#include<bits/stdc++.h>
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <map>
#include <stack>
#include <set>
#include <sstream>
#include <cmath>
#include <queue>
#include <deque>
#include <string>
#include <vector>
#define zeros(a) memset(a,0,sizeof(a))
#define ones(a) memset(a,-1,sizeof(a))
#define sc(a) scanf("%d",&a)
#define sc2(a,b) scanf("%d%d",&a,&b)
#define sc3(a,b,c) scanf("%d%d%d",&a,&b,&c)
#define scs(a) scanf("%s",a)
#define sclld(a) scanf("%I64d",&a)
#define pt(a) printf("%d\\n",a)
#define ptlld(a) printf("%I64d\\n",a)
#define rep(i,from,to) for(int i=from;i<=to;i++)
#define irep(i,to,from) for(int i=to;i>=from;i--)
#define Max(a,b) ((a)>(b)?(a):(b))
#define Min(a,b) ((a)<(b)?(a):(b))
#define lson (step<<1)
#define rson (lson+1)
#define eps 1e-6
#define oo (1e16)
#define TEST cout<<"*************************"<<endl
const double pi=4*atan(1.0);

using namespace std;
typedef long long ll;
template <class T> inline void read(T &n)
{
    char c; int flag = 1;
    for (c = getchar(); !(c >= \'0\' && c <= \'9\' || c == \'-\'); c = getchar()); if (c == \'-\') flag = -1, n = 0; else n = c - \'0\';
    for (c = getchar(); c >= \'0\' && c <= \'9\'; c = getchar()) n = n * 10 + c - \'0\'; n *= flag;
}
ll Pow(ll base, ll n, ll mo)
{
    if (n == 0) return 1;
    if (n == 1) return base % mo;
    ll tmp = Pow(base, n >> 1, mo);
    tmp = (ll)tmp * tmp % mo;
    if (n & 1) tmp = (ll)tmp * base % mo;
    return tmp;
}
//***************************

int n,m;
const int maxn=100000+10;
const ll mod=1000000007;
struct node
{
    int v,c;
    ll t,dis;
    node(){}
    node(int _v,int _c,ll _t,ll _dis)
    {
        v=_v,c=_c,t=_t,dis=_dis;
    }
    bool operator<(const node &a)const
    {
        if(dis==a.dis)
            return t>a.t;
        return dis>a.dis;
    }
};
vector<node>vt[maxn];
void dijkstra()
{
    ll ans=oo;
    priority_queue<node>q;
    for(int i=0;i<vt[1].size();i++)
    {
        vt[1][i].dis=vt[1][i].t;
        if(vt[1][i].v==n)
            ans=min(ans,vt[1][i].dis);
        q.push(vt[1][i]);
    }
    while(!q.empty())
    {
        node cur=q.top();
        q.pop();
        for(int i=0;i<vt[cur.v].size();i++)
        {
            node temp=vt[cur.v][i];
            if(temp.dis>cur.dis+temp.t+abs(cur.c-temp.c))
            {
                temp.dis=cur.dis+temp.t+abs(cur.c-temp.c);
                if(temp.v==n)
                    ans=min(ans,temp.dis);
                vt[cur.v][i]=temp;//非常重要，不要忘了这一步
                q.push(temp);
            }
        }
    }
    printf("%lld\\n",ans);
}
int main()
{
    #ifndef ONLINE_JUDGE
    //freopen("in.txt","r",stdin);
    #endif
    while(~sc2(n,m))
    {
        int a,b,c;
        ll t;
        for(int i=1;i<=n;i++)
            vt[i].clear();
        rep(i,1,m)
        {
            sc3(a,b,c);
            scanf("%lld",&t);
            vt[a].push_back(node(b,c,t,oo));
            vt[b].push_back(node(a,c,t,oo));
        }
        dijkstra();
    }
}