POJ 2349 Arctic Network

Arctic Network #include<stdio.h>#include<math.h>#include<algorithm>using namespace std;int father[550], m, k;double d[550];struct post{    double x, y;}p[550];struct edge{    int u, v;    double w;}e[500005];bool comp(edge e1, edge e2){    return  e1.w < e2.w;}double get_dis(double x1, double y1, double x2, double y2){    return sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2));}void Init(int n){    for(int i = 1; i <= n; i++)        father[i] = i;}int Find(int x){    if(x != father[x])        father[x] = Find(father[x]);    return father[x];}void Merge(int a, int b){    int p = Find(a);    int q = Find(b);    if(p > q)        father[p] = q;    else        father[q] = p;}void Kruskal(int n){    k = 0;    double Max = 0;    for(int i = 0; i < m; i++)        if(Find(e[i].u) != Find(e[i].v))        {            Merge(e[i].u, e[i].v);            d[k++] = e[i].w;            n--;            if(n == 1)                return;        }}int main(){    int t, S, P, i, j;    double x, y;    scanf("%d",&t);    while(t--)    {        m = 0;        scanf("%d%d",&S,&P);        Init(P);        for(i = 1; i <= P; i++)            scanf("%lf%lf",&p[i].x, &p[i].y);        for(i = 1; i <= P; i++)            for(j = i + 1; j <= P; j++)            {                e[m].u = i;                e[m].v = j;                e[m++].w = get_dis(p[i].x, p[i].y, p[j].x, p[j].y);                e[m].u = j;                e[m].v = i;                e[m++].w = get_dis(p[i].x, p[i].y, p[j].x, p[j].y);            }        sort(e, e+m, comp);        Kruskal(P);        printf("%.2lf\n",d[P-S-1]);    }    return 0;}