这是克鲁斯卡尔算法的正确实现吗？

我编写了以下代码作为UVA OnlineJudge问题#10034的解决方案：

// problem 10034
#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <iomanip>
using namespace std;
class tree;
class vertex {
public:
    double x,y;
    tree* mTree;
};
class tree {
public:
    tree(tree* last,vertex* v);
    int size();
    void assimilate(tree* other);
    tree* prev;
    tree* next;
    vector<vertex*> vertices;
};
tree::tree(tree* last,vertex* v) {
    prev = last;
    next = NULL;
    vertices.push_back(v);
    v->mTree = this;
    if(last != NULL) {
        last->next = this;
    }
}
int tree::size() {
    return vertices.size();
}
void tree::assimilate(tree* other) {
    int c;
    if(other->prev != NULL) {
    other->prev->next = other->next;
    }
    if(other->next != NULL) {
    other->next->prev = other->prev;
    }
    for(c = 0;c < other->vertices.size();c++) {
        this->vertices.push_back(other->vertices[c]);
        other->vertices[c]->mTree = this;
    }
    delete other;
}
class edge {
public:
    edge() {
        v1 = NULL;
        v2 = NULL;
        weight = 0;
    }
    edge(vertex* a,vertex* b,double w) {
        v1 = a;
        v2 = b;
        weight = w;
    }
    bool operator<(const edge& rhs) const {
        return this->weight < rhs.weight;
    }
    vertex* v1;
    vertex* v2;
    double weight;
};
double dist(double x1,double y1,double x2,double y2) {
    double dx;
    double dy;
    dx = x2 - x1;
    dy = y2 - y1;
    return sqrt((dx*dx) + (dy*dy));
}
int main() {
    int ncases;
    int ccase;
    int c;
    int nverts;
    int nedges;
    edge* edges;
    vertex* vertices;
    tree* lasttree;
    double cost;
    tree* t1;
    tree* t2;
    bool treeexists;
    int cedge;
    int cc;

    cin>>ncases;
    for(ccase = 0;ccase < ncases;ccase++) {
        cin>>nverts;
        nedges = (nverts*(nverts-1)) / 2;
        treeexists = false;
        lasttree = NULL;
        vertices = new vertex[nverts];
        edges = new edge[nedges];
        cedge = 0;
        for(c = 0;c < nverts;c++) {
            cin>>vertices[c].x;
            cin>>vertices[c].y;
            lasttree = new tree(lasttree,&vertices[c]);
        }
        for(c = 0;c < nverts;c++) {
            for(cc = c+1;cc < nverts;cc++) {
                edges[cedge] = edge(vertices+c,vertices+cc,dist(vertices[c].x,vertices[c].y,vertices[cc].x,vertices[cc].y));
                cedge++;
            }
        }
        sort(edges,edges+nedges);
        cost = 0;
        for(c = 0;c < nedges;c++) {
            //cout<<"edge with length "<<edges[c].weight<<endl;
            if(edges[c].v1->mTree != edges[c].v2->mTree) {
                //cout<<"using"<<endl;
                cost += edges[c].weight;
                t1 = edges[c].v1->mTree;
                t2 = edges[c].v2->mTree;
                if(t1->size() > t2->size()) {
                    t1->assimilate(t2);
                } else {
                    t2->assimilate(t1); 
                }
            }
        }
        if(ccase > 0) {
            cout<<endl;
        }
        cout<<fixed<<setprecision(2)<<cost;
        delete vertices[0].mTree;
        delete[] vertices;
        delete[] edges;
    }
    return 0;
}

它适用于问题提供的测试用例和我在这里找到的更大的测试用例：http://online-judge.uva.es/board/viewtopic.php?p=21939#p21939

但是，当我将其提交给UVA时，我收到错误的答案消息。我对 Krukar 算法的实现是否正确？我做错了什么？