【HDU1162】Eddy's picture（MST基础题）

很基础的点坐标MST，一不留神就AC了， - - ！！

#include <iostream>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <cmath>
#include <cctype>
#include <algorithm>
#include <numeric>
#include <limits.h>

#define typec double
using namespace std;

const int inf = 0xffff;
const int V = 105;
int vis[V];
typec lowc[V], Map[V][V], point[V][2];

typec prim (typec cost[][V], int n) {
    int i, j, p;
    typec minc, res = 0;
    memset(vis, 0, sizeof(vis));
    vis[0] = 1;
    for (i = 1; i < n; ++ i) lowc[i] = cost[0][i];
    for (i = 1; i < n; ++ i) {
        minc = inf;
        p = -1;
        for (j = 0 ; j < n; ++ j) {
            if (0 == vis[j] && minc > lowc[j]) {
                minc = lowc[j];
                p = j;
            }
        }
        if (inf == minc) return -1;
        res += minc;
        vis[p] = 1;
        for (j = 0 ; j < n; ++ j) {
            if (0 == vis[j] && lowc[j] > cost[p][j]) {
                lowc[j] = cost[p][j];
            }
        }
    }
    return res;
}

double cal_dis (double x1, double y1, double x2, double y2) {
    return sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}

int main () {
    int n;
    while (~scanf("%d", &n)) {

        for (int i = 0 ; i < n; ++ i) {
            scanf("%lf %lf", &point[i][0], &point[i][1]);
        }

        for (int i = 0 ; i < V; ++ i) {
            for (int j = 0; j < V; ++ j) {
                if (i == j) Map[i][j] = 0;
                else Map[i][j] = inf;
            }
        }

        for (int i = 0; i < n; ++ i) {
            for (int j = i + 1; j < n; ++ j) {
                Map[i][j] = Map[j][i] =
                    cal_dis(point[i][0], point[i][1], point[j][0], point[j][1]);
            }
        }

        //cout << prim(Map, n) << endl;
        printf("%.2lf
", prim(Map, n));
    }
    return 0;
}