UVA10397 - Connect the Campus（最小生成树+并查集）

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UVA10397 - Connect the Campus（最小生成树）

题目链接

题目大意：给你n个点，然后再给你m个已经连接的边，问如何使得所有的点都相连并且新建的边长度之和最小。

解题思路：最小生成树，但是有m条边是已经建好的，就将这些边的权值变成0，然后用kruskal的方法来求长度。

代码：

#include <cstdio>#include <cmath>#include <cstring>#include <algorithm>using namespace std;const int maxn = 755;const int maxm = 3e5;struct Node {    int x, y;}node[maxn];double w[maxm];int p[maxn], u[maxm], v[maxm];int vis[maxn][maxn], r[maxm];double dist (int i, int j) {    double x = node[i].x - node[j].x;    double y = node[i].y - node[j].y;    return sqrt(x * x + y * y);}void init (int n) {     for (int i = 0; i < n; i++)        p[i] = i;}int getParent (int x) {    return (x == p[x]) ? p[x] : p[x] = getParent(p[x]);}int cmp (int i, int j) {    return w[i] < w[j];}double Kruskal (int n, int m) {    double ans = 0;    init(n);    for (int i = 0; i < m; i++)        r[i] = i;    sort(r, r + m, cmp);    for (int i = 0; i < m; i++) {        int P = getParent(u[r[i]]);        int Q = getParent(v[r[i]]);        if (P == Q) continue;        ans += w[r[i]];        p[P] = Q;    }    return ans;}int main () {    int n, m;    while (scanf ("%d", &n) != EOF) {        for (int i = 0; i < n; i++)             scanf ("%d%d", &node[i].x, &node[i].y);         int x, y;        memset (vis, 0, sizeof(vis));        scanf ("%d", &m);           for (int i = 0; i < m; i++) {            scanf ("%d%d", &x, &y);            vis[x - 1][y - 1] = vis[y - 1][x - 1] = 1;        }        int pos = 0;        for (int i = 0; i < n; i++)            for (int j = i + 1; j < n; j++) {                u[pos] = i;                v[pos] = j;                if (vis[i][j])                    w[pos++] = 0;                else                    w[pos++] = dist(i, j);            }        printf ("%.2lf\n", Kruskal(n, pos));        }    return 0;}

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