poj1751

最小生成树

#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <cmath>
using namespace std;

#define maxn 800
#define maxm 1000

struct Point
{
    int x, y;
}point[maxn];

struct Edge
{
    int a, b;
}edge[maxn * maxn];

int n, m;
int father[maxn];

int dist(Point a, Point b)
{
    Point p;
    p.x = a.x - b.x;
    p.y = a.y - b.y;
    return p.x * p.x + p.y * p.y;
}

bool operator < (const Edge &a, const Edge &b)
{
    return dist(point[a.a], point[a.b]) < dist(point[b.a], point[b.b]);
}

int getanc(int a)
{
    if (a == father[a])
        return a;
    return father[a] = getanc(father[a]);
}

void merge(int a, int b)
{
    father[getanc(a)] = getanc(b);
}

void input()
{
    scanf("%d", &n);
    for (int i = 0; i < n; i++)
        scanf("%d%d", &point[i].x, &point[i].y);
    for (int i = 0; i < n; i++)
        father[i] = i;
    scanf("%d", &m);
    for (int i = 0; i < m; i++)
    {
        int a, b;
        scanf("%d%d", &a, &b);
        a--;
        b--;
        merge(a, b);
    }
    m = 0;
    for (int i = 0; i < n - 1; i++)
        for (int j = i + 1; j < n; j++)
        {
            edge[m].a = i;
            edge[m].b = j;
            m++;
        }
}

void work()
{
    for (int i = 0; i < m; i++)
        if (getanc(edge[i].a) != getanc(edge[i].b))
        {
            int a = edge[i].a;
            int b = edge[i].b;
            merge(a, b);
            printf("%d %d\n", a + 1, b + 1);
        }
}

int main()
{
    //freopen("t.txt", "r", stdin);
    input();
    sort(edge, edge + m);
    work();
    return 0;
}