ACM-ICPC 2018 沈阳赛区网络预赛 D. Made In Heaven（第k短路模板）

求第k短路模板

先逆向求每个点到终点的距离，再用dij算法，不会超时（虽然还没搞明白为啥。。。

#include<iostream>
#include<cstdio> 
#include<cmath>
#include<queue>
#include<vector>
#include<string.h>
#include<cstring>
#include<algorithm>
#include<set>
#include<map>
#include<fstream>
#include<cstdlib>
#include<ctime>
#include<list>
#include<climits>
#include<bitset>
#include<random>
#include <ctime>
#include <cassert>
#include <complex>
#include <cstring>
#include <chrono>
using namespace std;
#define fio ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define fopen freopen("input.in", "r", stdin);freopen("output.in", "w", stdout);
#define left asfdasdasdfasdfsdfasfsdfasfdas1
#define tan asfdasdasdfasdfasfdfasfsdfasfdas
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
typedef long long ll;
typedef unsigned int un;
const int desll[4][2]={{0,1},{0,-1},{1,0},{-1,0}};
const int mod=1e9+7;
const int maxn=1e3+7;
const int maxm=1e5+7;
const double eps=1e-8;
int n,k,m;
int ar[maxn];
int head[maxn],sz,rehead[maxn];
bool vis[maxn];
int dis[maxn];
struct node
{
    int b,nex,c;
}no[maxn*10],reno[maxn*10];
void add(int a,int b,int c)
{
    no[sz].b=b;
    no[sz].c=c;
    no[sz].nex=head[a];
    head[a]=sz;
    reno[sz].b=a;
    reno[sz].c=c;
    reno[sz].nex=rehead[b];
    rehead[b]=sz++;
}
struct state{
    int all,pre,v;
    state(int a,int b,int c){
        all=a;pre=b;v=c;
    }
    state(){
        
    }
    bool operator<(const state& s)const{
        return all>s.all;
    }
};
priority_queue<state> qu;
void init(int s,int e)
{
    memset(vis,0,sizeof(vis));
    memset(dis,-1,sizeof(dis));
    queue<int> qu;
    qu.push(e);vis[e]=1;
    dis[e]=0;
    while(qu.size()){
        int x=qu.front();
        qu.pop();
        vis[x]=0;
        for(int i=rehead[x];i!=-1;i=reno[i].nex){
            int v=reno[i].b;
            if(dis[v]==-1 || dis[v]>dis[x]+reno[i].c){
                dis[v]=dis[x]+reno[i].c;
                if(vis[v]==0){
                    vis[v]=1;
                    qu.push(v);
                }
            }
        }
    }
}
int main()
{
    while(scanf("%d%d",&n,&m)!=EOF){
        int s,e,k,t;
        scanf("%d%d%d%d",&s,&e,&k,&t);
        memset(head,-1,sizeof(head));
        memset(rehead,-1,sizeof(rehead));sz=0;
        for(int i=0;i<m;i++){
            int a,b,c;scanf("%d%d%d",&a,&b,&c);
            add(a,b,c);
        }
        int ans=0;
        init(s,e);
        //for(int i=1;i<=n;i++)cout<<dis[i]<<" ";cout<<endl;
        if(dis[s]==-1)ans=-1;
        else{
            while(qu.size())qu.pop();
            qu.push(state(dis[s],0,s));
            state mid;
            int ins=0;
            while(qu.size()){
                mid = qu.top();
                qu.pop();
                if(mid.v==e){
                    ins++;
                    if(ins==k){
                        ans=mid.all;
                        break;
                    }
                }
                for(int i=head[mid.v];i!=-1;i=no[i].nex){
                    int v=no[i].b;
                    qu.push(state(mid.pre+no[i].c+dis[v],mid.pre+no[i].c,v));
                }
            }
        }
        if(ans!=-1 && ans<=t)printf("yareyaredawa
");
        else printf("Whitesnake!
");
    }
    return 0;
}