ZOJ 1372 / POJ 1287 Networking ( kruskal+prim )

史上第二水最小生成树。

 

我刚开始是想练练prim算法，没想到是段错误，我感觉自己的算法没什么错误，就把提交到了poj上，没想到AC了，晕倒。没办法，上网搜了一下数据，测试之后发现竟然答案全部正确，faint~~果断换kruskal，用priority_queue，一次过，哎~~~

 

有人知道我prim哪里错了的说一声啊。。。。。

 

KRUSKAL：

#include<iostream> #include<string> #include<queue> typedef struct { int from,to,w; } node;node t; struct cmp { bool operator() (const node a,const node b) {return a.w > b.w;} }; int p[51]; int find(int i) {return p[i]==i?i:p[i]=find(p[i]);} const int INF = 90000990; using namespace std; int main(void) { priority_queue<node,vector<node>,cmp> q; int dist[51],flag[51]; int n,m; int j,i,k; int from,to,w; int sum,min,now; while( cin >> n >> m ) { if( n == 0 ) break; while(!q.empty() ) q.pop(); for( i = 1; i <= n; i++ ) p[i] = i; for( i = 1; i <= m; i++ ) { cin >> t.from >> t.to >> t.w; q.push(t); } sum = 0; while( !q.empty() ) { t = q.top();q.pop(); from = t.from; to = t.to; from = find(from); to = find(to); if( from != to ) {sum += t.w;p[from]=to;} } cout << sum << endl; } return 0; }

 

 

 

PRIM：

#include<iostream> #include<string> const int INF = 90000990; using namespace std; int main(void) { int map[51][51],dist[51],flag[51]; int n,m; int j,i,k; int from,to,w; int sum,min,now; while( cin >> n >> m ) { if( n == 0 ) break; for( i = 1; i <= n; i++ ) { dist[i] = INF; flag[i] = 0; for( j = 1; j <= n; j++ ) map[i][j] = INF; } for( i = 1; i <= m; i++ ) { cin >> from >> to >> w; if( w < map[from][to] ) map[from][to]=map[to][from]=w; } dist[from] = sum = 0; flag[now = from] = 1; for( i = 1; i < n; i++ ) { for( j = 1; j <= n; j++ ) if( !flag[j] && map[now][j] < dist[j] ) dist[j] = map[now][j]; for( j = 1,min = INF; j <= n; j++ ) if( !flag[j] && dist[j] < min ) min = dist[now = j]; sum += min;flag[now] = 1; } cout << sum << endl; } return 0; }