洛谷P1339 [USACO09OCT]热浪Heat Wave

2017-03-18

题目：https://www.luogu.org/problem/show?pid=1339

相当于spfa的入门题了吧。

spfa不会的同学，这个教程不错：http://www.360doc.com/content/13/1208/22/14357424_335569176.shtml

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<queue>
using namespace std;

struct node{
    int value;
    int to;
    node *next;
};

const int maxn=10000;
int t,c,ts,te;
int dist[maxn];
int re,rs,ci;
node* line[maxn];
queue<int> q;

void spfa(int src){
    node *tmp;
    int now;
    q.push(src);
    dist[src]=0;
    while (!q.empty()){
        now=q.front();
        q.pop();
        tmp=line[now]->next;
        while (tmp){
            if (dist[tmp->to]>dist[now]+tmp->value){
                dist[tmp->to]=dist[now]+tmp->value;
                q.push(tmp->to);
            }
            tmp=tmp->next;
        }
    }
}

int main(){
    //freopen("heatwave.in","r",stdin);
    //freopen("heatwave.out","w",stdout);
    scanf("%d%d%d%d",&t,&c,&ts,&te);
    node *tmp;
    for (int i=1;i<=t;++i){
        dist[i]=maxn;
        line[i]=new node;
        line[i]->next=NULL;
    }
    for (int i=1;i<=c;++i){
        tmp=new node;
        scanf("%d%d%d",&rs,&re,&ci);
        
        tmp->to=re;
        tmp->value=ci;
        tmp->next=line[rs]->next; 
        line[rs]->next=tmp;
        
        
        tmp=new node;
        tmp->to=rs;
        tmp->value=ci;
        tmp->next=line[re]->next;
        line[re]->next=tmp;
    }
    
    spfa(ts);
    
    cout<<dist[te];
    //fclose(stdin);
    //fclose(stdout);
    return 0;
}

骗分真神奇，暴力出奇迹。