CCF_201612-4_交通规划

Posted 2020-08-19 冷暖知不知

http://115.28.138.223/view.page?gpid=T44

 

好像也没想象中的那么难，没办法，当初连个优先队列dij都不会写= =

在优先队列dij算法上加上相等的时候的处理就可以了。

 

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

struct node
{
    int pos,cost;
    node(int a,int b):pos(a),cost(b){};
    friend bool operator <(node x,node y)
    {
        return x.cost > y.cost;
    }
};
struct edge
{
    int to,cost;
    edge(int a,int b):to(a),cost(b){};
};
vector<edge> v[10005];
bool vis[10005] = {0};
int dis[10005],cost[10005],n,m;

void dij()
{
    memset(dis,0x3f,sizeof(dis));
    memset(cost,0x3f,sizeof(cost));
    dis[0] = 0;
    cost[0] = 0;
    priority_queue<node> q;
    q.push(node(1,0));
    while(!q.empty())
    {
        int now = q.top().pos;
        if(vis[now])    continue;
        vis[now] = 1;
        for(int i = 0;i < v[now].size();i++)
        {
            int to = v[now][i].to,c = v[now][i].cost;
            if(vis[to]) continue;
            if(dis[to] > dis[now]+c)
            {
                dis[to] = dis[now]+c;
                cost[to] = c;
                q.push(node(to,dis[to]));
            }
            else if(dis[to] == dis[now]+c)    cost[to] = min(cost[to],c);
        }
    }
}

int main()
{
    scanf("%d%d",&n,&m);
    for(int i = 1;i <= m;i++)
    {
        int a,b,c;
        scanf("%d%d%d",&a,&b,&c);
        v[a].push_back(edge(b,c));
        v[b].push_back(edge(a,c));
    }
    dij();
    int ans = 0;
    for(int i = 2;i <= n;i++)   ans += cost[i];
    printf("%d\n",ans);
    return 0;
}