UVA 10397 Connect the Campus

MST 比较水。给出的M个直接合并就好。边权就还是DIST；

或者直接M个点对的边权直接设置为0

#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <stack>
#include <queue>
#include <cctype>
#include <cstdio>
#include <string>
#include <vector>
#include <climits>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>
#define LL long long
#define PI 3.1415926535897932626
using namespace std;
int gcd(int a, int b) {return a % b == 0 ? b : gcd(b, a % b);}
#define MAXN 755
int p[MAXN];
int N,M,cas;
int Find(int x) {return x == p[x] ? x : p[x] = Find(p[x]);}
struct node
{
    int x,y;
}src[MAXN];
struct dis
{
    int u,v;
    double dist;
    friend bool operator < (const dis &a,const dis &b)
    {
        return a.dist < b.dist;
    }
}d[MAXN*MAXN];
void read()
{
    cas = 0;
    for (int i = 1; i <= N; i++)
        scanf("%d%d",&src[i].x,&src[i].y);
    for (int i = 1; i <= N; i++)
        for (int j = i + 1; j <= N; j++)
    {
        d[cas].u = i;
        d[cas].v = j;
        d[cas++].dist = sqrt((double)((src[j].x - src[i].x) * (src[j].x - src[i].x)) + (double)((src[j].y - src[i].y) * (src[j].y - src[i].y)));
    }
    sort(d,d + cas);
    scanf("%d",&M);
    for (int i = 0; i <= N; i++) p[i] = i;
    while (M--)
    {
        int u,v;
        scanf("%d%d",&u,&v);
        int x = Find(u) , y = Find(v);
        if (x != y) p[x] = y;
    }
}
double kruskal()
{
    double ans = 0;
    for (int i = 0; i < cas; i++)
    {
        int u = d[i].u , v = d[i].v ;
        double w = d[i].dist;
        int x = Find(u) , y = Find(v);
        if (x != y)
        {
            ans += w;
            p[x] = y;
        }
    }
    return ans;
}
int main()
{
    while (scanf("%d",&N) != EOF)
    {
        read();
        printf("%.2lf
",kruskal());
    }
    return 0;
}