prime模板

/*prime模板，时间复杂度o(v^2)*/#include <cstdio>#include <cstring>#define N 1005#define INF 0x3f3f3f3fint map[N][N], dis[N], vis[N];int n, m;int cnt = 0, sum = 0;void init(){for (int i = 1; i <= n; i++){for (int j = 1; j <= n; j++){if (i == j)map[i][j] = 0;else map[i][j] = INF;}}return;}void creatgraph(){int i, j, w;for (int k = 0; k < m; k++){scanf("%d%d%d", &i, &j, &w);if (map[i][j] > w)//重边取最小map[i][j] = map[j][i] = w;//无向图}return;}int prime(int start){for (int i = 1; i <= n; i++)//dis存储节点1到其他各个节点的距离，达不到用INF表示dis[i] = map[start][i];cnt++;memset(vis, 0, sizeof(vis));vis[start] = 1;//记下第一个节点while (cnt < n){int min = INF, j = -1;for (int i = 1; i <= n; i++)//找当前生成树加一个节点所需的最小权值min，并记录该节点{if (!vis[i] && dis[i] < min){min = dis[i];j = i;}}if (min == INF) return -1;//图不连通vis[j] = 1; cnt++; sum += min;//标记新节点，累加最小权值/*下边更新dis数组,根据新节点到各个未知节点的距离来更新*/for (int k = 1; k <= n; k++){if (!vis[k] && dis[k] > map[j][k])dis[k] = map[j][k];}}return sum;}int main(){while (scanf("%d%d", &n, &m) != EOF)//输入顶点数和边数{int ans = 0;cnt = 0; sum = 0;//cnt表示生成树的顶点个数，sum存储路径和init();//初始化图creatgraph();//建图int start;//scanf("%d", &start);ans = prime(1);//核心算法if (ans != -1)printf("%d\n", ans);elseprintf("图不连通,最小生成树不存在\n");}return 0;}