XDOJ_1069_最小生成树

Posted 2020-08-18

http://acm.xidian.edu.cn/problem.php?id=1069

 

巧妙的方法构成图，最小生成树模版。

 

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

struct line
{
    int to,w;
    line(int a,int b):to(a),w(b){}
    friend bool operator<(line X,line Y)
    {
        return X.w > Y.w;
    }
};

int n,m,k,x,dis[20005],vis[20005];
vector<line> v[20005];

int prim()
{
    memset(vis,0,sizeof(vis));
    memset(dis,0x3f,sizeof(dis));
    int ans = 0,cnt = 0;
    priority_queue<line> q;
    q.push(line(0,0));
    int endd = n+m;
    while(cnt <= endd && !q.empty())
    {
        while(!q.empty() && vis[q.top().to])    q.pop();
        ans += q.top().w;
        int now = q.top().to;
        vis[now] = 1;
        cnt++;
        for(int i = 0;i < v[now].size();i++)
        {
            if(vis[v[now][i].to])   continue;
            if(dis[v[now][i].to] <= v[now][i].w)   continue;
            dis[v[now][i].to] = v[now][i].w;
            q.push(line(v[now][i].to,v[now][i].w));
        }
    }
    return ans;
}

int main()
{
    int T;
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d%d%d%d",&m,&n,&k,&x);
        int endd = n+m;
        for(int i = 0;i <= endd;i++) v[i].clear();
        for(int i = 1;i <= endd;i++) v[0].push_back(line(i,k));
        while(x--)
        {
            int a,b,c;
            scanf("%d%d%d",&a,&b,&c);
            a += 1;
            b += m+1;
            c = k-c;
            v[a].push_back(line(b,c));
            v[b].push_back(line(a,c));
        }
        printf("%d\n",prim());
    }
    return 0;
}