CCF201609-4 交通规划

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

#define maxn 10007
//使用了prim算法
struct Node{
Node(){}
int v; //节点
int c; //花费
Node(int a, int b){
    v = a;
    c = b;
}
};

vector <Node> g[maxn];
int dist[maxn];     //每个节点最合适的花费
int cost[maxn];     //每个花费
int flag[maxn];     //是否已经连接

bool operator <(Node a,Node b){
    if(a.c==b.c) return a.v<b.v;
    return a.c<b.c;
}

int prime(int s, int n){
    memset(flag,0,sizeof(flag));
    dist[s] = 0;
    cost[s] = 0;
    Node now,add;
    now.v = s;
    now.c = 0;
    queue <Node> Q;
    Q.push(now);
    while(Q.size()>0){
        now = Q.front();
        Q.pop();
        if(flag[now.v])continue;
        flag[now.v] = 1;
        for(int i=0; i<g[now.v].size(); i++){//对连接的点进行遍历，找花费最小的情况

            add.v = g[now.v][i].v;  //选中点所连接的点
            add.c = now.c + g[now.v][i].c; //所需要的花费
            if(flag[add.v]==0&&dist[add.v]>=add.c){ //若该点还未连接且花费小于之前插入的点
                dist[add.v] = add.c;
            Q.push(add);
            cost[add.v] = min(cost[add.v],g[now.v][i].c);
            }
        }
    }
    int ans = 0;
    for(int i=1; i<=n ;i++)
        ans += cost[i];
    return ans;

}
int main(){

int n,m;
scanf("%d%d",&n,&m);
memset(cost,0x3f3f3f,sizeof(cost));
memset(dist,0x3f3f3f,sizeof(dist));

int u,v,c;

for(int i=0; i<m; i++)
{
    scanf("%d%d%d",&u,&v,&c);
    g[u].push_back(Node(v,c)); //插入相应的点，并且数组存入连接的点
    g[v].push_back(Node(u,c));
}
cout<<prime(1,n)<<endl;
return 0;

}