P3366【模板】最小生成树

P3366【模板】最小生成树

Kruskal

 #include <bits/stdc++.h>
 using namespace std;
 typedef long long ll;
 const int maxn = ;
 int fa[maxn], n, m, ans = ;
 bool flag = false;  // 判断图是否连通
 struct edge {
     int u, v, w;
 }eds[];
 bool cmp(const edge x, const edge y) {
     return x.w < y.w;
 }
 int find(int x) {
     if (x != fa[x]) fa[x] = find(fa[x]);
     return fa[x];
 }
 void kruskal() {
     int cnt = ;
     sort(eds+,eds++m,cmp);
     for (int i = ; i <= m; i++) {
         int fx = find(eds[i].u);
         int fy = find(eds[i].v);
         if (fx == fy) continue;
         ans += eds[i].w;
         fa[fx] = fy;
         if (++cnt == n-) {
             flag = true;
             break;
         }
     }
 }
 int main() {
     scanf("%d%d",&n,&m);
     for (int i = ; i <= m; i++)
         scanf("%d%d%d",&eds[i].u,&eds[i].v,&eds[i].w);
     for (int i = ; i <= n; i++) fa[i] = i;
     kruskal();
     if (flag) printf("%d\n",ans);
     else puts("orz");
     return ;
 }

Prim+堆优化

 #include <bits/stdc++.h>
 using namespace std;
 const int maxn = ;
 struct edge{
     int u, dis;
     bool operator < (const edge &tmp) const { return dis > tmp.dis; }
 };
 priority_queue<edge> que;
 bool vis[maxn];
 int n, m, ans, dis[maxn];
 vector<edge> ve[maxn];  // 邻接链表
 int main(){
     memset(dis,0x3f3f3f3f,sizeof(dis));
     scanf("%d%d",&n,&m);
     for(int i = ; i <= m; i++) {
         int u, v, w; scanf("%d%d%d",&u,&v,&w);
         ve[u].push_back(edge{v,w});
         ve[v].push_back(edge{u,w});
     }

     dis[] = ; que.push((edge){,});
     int k = ;
     while(!que.empty()&& k<n){
         edge x = que.top(); que.pop();
         if(vis[x.u]) continue;
         vis[x.u] = true; ++k; ans += x.dis;
         for (int i = ; i < ve[x.u].size(); i++) {
             int to = ve[x.u][i].u, d = ve[x.u][i].dis;
             if (dis[to] > d)
                 dis[to] = d, que.push((edge){to,d});
         }
     }
     if (k < n) puts("orz");
     else printf("%d",ans);
     return ;
 }