HDU 1875 畅通工程再续

地址

mst入门题，根据各个点坐标建N*(N-1)/2个边的图。

#include <iostream>
#include <algorithm>
#include <cstring>
#include <vector>
#include <utility>
#include <cmath>
using namespace std;

const int INF = 1e9;
const int MAXC = 1e2 + 5;
int T, C;
int x[MAXC];
int y[MAXC];
vector<pair<int, double>> v[MAXC];
double d[MAXC];
double ans;
bool vis[MAXC];

void init_edge()
{
    for (int i = 0; i < C - 1; i++)
    {
        for (int j = i + 1; j < C; j++)
        {
            double w = sqrt(double(pow(x[i] - x[j], 2) + pow(y[i] - y[j], 2)));
            if (w >= 10.0 && w <= 1000.0)
            {
                v[i].push_back(make_pair(j, w));
                v[j].push_back(make_pair(i, w));
            }
        }
    }
}

void prim(int s)
{
    d[s] = 0;                                      // 没搞明白prim的堆优化，先不来了，不过想用priority_queue中的greater<int>要加头文件functional
    for (int i = 0; i < C; i++)
    {
        double mind = INF;
        int u = -1;
        for (int j = 0; j < C; j++)
        {
            if (!vis[j] && d[j] < mind)
            {
                mind = d[j];
                u = j;
            }
        }
        if (u == -1)
        {
            ans = -1;
            return;
        }
        ans += mind;
        vis[u] = true;
        for (int j = 0; j < v[u].size(); j++)
        {
            int k = v[u][j].first;
            double w = v[u][j].second;
            if (!vis[k] && w < d[k])
            {
                d[k] = w;
            }
        }
    }
}

int main()
{
    scanf("%d", &T);
    for (; T--;)
    {
        scanf("%d", &C);
        fill(d, d + C, INF);
        fill(vis, vis + C, false);
        ans = 0;
        for (int i = 0; i < C; i++)
        {
            scanf("%d%d", &x[i], &y[i]);
            v[i].clear();                            // 排错
        }
        init_edge();
        prim(0);
        if (ans == -1.0) printf("oh!\n");
        else printf("%.1f\n", ans * 100.0);
    }

    return 0;
}