poj1258 Agri-Net （prim+heap）

题目链接：poj1258 Agri-Net

这题我上个月做过，是个大水题，今天看见有人用prim+heap做的，就学习了下。

 1 #include<cstdio>
 2 #include<cstring>
 3 #include<algorithm>
 4 #include<queue>
 5 #include<vector>
 6 #include<set>
 7 #define CLR(a,b) memset((a),(b),sizeof((a)))
 8 using namespace std;
 9
10 const int inf = 0x3f3f3f3f;
11 const int N = 101;
12 int low[N], s[N];
13 int n, ans, num;
14 struct Edge{
15     int v,c;
16     Edge(int _v=0,int _c=0):v(_v),c(_c){}
17     bool operator < (const Edge&r)const{
18         return r.c < c;
19     }
20 };
21 vector<Edge>g[N];
22
23 int prim_heap(){
24     priority_queue<Edge>q;
25     int i, u, v, w;
26     Edge p;
27     ans = 0;//最小生成树总权值
28     num = 0;//已加入最小生成树的顶点数目
29     q.push(Edge(0, 0));
30     while(!q.empty() && num < n){
31         p = q.top(); q.pop();
32         u = p.v;
33         if(s[u]) continue;
34         s[u] = 1;
35         ans += p.c;
36         num++;
37         for(i = 0; i < g[u].size(); ++i){
38             v = g[u][i].v;
39             if(s[v] == 0){
40                 w = g[u][i].c;
41                 if(w < low[v]){
42                     low[v] = w;
43                     q.push(Edge(v, w));
44                 }
45             }
46         }
47     }
48     if(num < n)
49         return -1;
50     return ans;
51 }
52 int main(){
53     int i, j, x;
54     while(scanf("%d", &n) == 1){
55         for(i = 0; i < n; ++i)
56             g[i].clear();
57         for(i = 0; i < n; ++i)
58             for(j = 0; j < n; ++j){
59                 scanf("%d", &x);
60                 g[i].push_back(Edge(j, x));
61         }
62         CLR(s, 0); CLR(low, inf);
63         printf("%d\n",prim_heap());
64     }
65     return 0;
66 }