HDU-1863- 畅通工程(最小生成树，prim)

题目链接

题意:裸的最小生成树

#include<cstdio>#include<cmath>#include<cstring>#include<algorithm>#include<iostream>#include<time.h>#include<set>#include<stack>#include<vector>#include<map>#define pi acos(-1)#define maxn 111111#define maxm 11111#define INF 0x3F3F3F3F#define eps 1e-8#define pb push_back#define mem(a) memset(a,0,sizeof a)using namespace std;const long long mod = 1000000007;/**lyc**/int n, m;int mp[222][222];int vis[222];int cost[222];void init(void) {    memset(mp, INF, sizeof mp);    for (int i = 0; i <= 111; i++) {        mp[i][i] = 0;    }    memset(vis, 0, sizeof vis);    memset(cost, INF, sizeof cost);}int Prim() {    cost[1] = 0;    vis[1] = 1;    int ans = 0;    for (int i = 2; i <= n; i++) {        cost[i] = mp[1][i];    }    for (int i = 1; i < n; i++) {        int minx = INF;        int pos = 0;        /**找离集合最近的点**/        for (int j = 1; j <= n; j++) {            if (!vis[j] && cost[j] < minx) {                minx = cost[j];                pos = j;            }        }        //cout << pos << endl;        if (pos == 0) {            return -1;        }        ans += cost[pos];        vis[pos] = 1;        /**加入并修改**/        for (int j = 1; j <= n; j++) {            if (!vis[j] &&  mp[pos][j] < cost[j]) {                  //这里注意，已经把pos点给加入了，所以直接算，不用加原来的了                cost[j] = mp[pos][j];            }        }    }    return ans;}int main() {    while (scanf("%d%d", &m, &n) && (m != 0)) {        init();        int a, b, x;        for (int i = 1; i <= m; i++) {            scanf("%d%d%d", &a, &b, &x);            mp[a][b] = mp[b][a] = x;        }        //cout << "***" << endl;        int ans = Prim();        if (ans == -1) {            printf("?\n");        }        else {            printf("%d\n", ans);        }    }    return 0;}