kruskal基础算法

/*Kruskal算法1:将所有边按照从小到大的顺序排列2:依次将权值最小的边加入生成树的子集当中3:重复以上的步骤直到找出n-1条边为止注：Kruskal适合求稀疏图问题，而prim算法适合求稠密图问题*/#include <iostream>#include <cstdio>#include <algorithm>#include <vector>using namespace std;const int maxn = 1000 + 10;int n, m, parent[maxn], childNum[maxn], sum;struct Edge {    int u, v, val;} edge[maxn];vector<Edge> ans;bool cmp(const Edge & s1, const Edge & s2) {    return s1.val < s2.val;}int UFind(int u) {    return parent[u] == u ? u : UFind(parent[u]);}bool join(int u, int v) {    int root1 = UFind(u);    int root2 = UFind(v);    if(root1 == root2)  return false;   //存在环    if(childNum[root1] > childNum[root2]) {     //将节点数少的点连接到节点数量多的树上面        parent[root2] = root1;        childNum[root1] += childNum[root2];    }    else {        parent[root1] = root2;        childNum[root2] += childNum[root1];    }}bool kruskal() {    sort(edge, edge + m, cmp);    int sideNum = 0;    //边的个数    for(int i = 0; i < m; i++) {        if(join(edge[i].u, edge[i].v)) {            sideNum++;            sum += edge[i].val;            ans.push_back(edge[i]);        }        if(sideNum == n - 1)    return true;    //如果边的个数到达n-1条，则最小生成树的构建完成    }    return false;}int main(){    cout << "enter the number of vertexes and sides:" << endl;    cin >> n >> m;    for(int i = 0; i < n; i++) {    //初始化        parent[i] = i;        childNum[i] = 1;    }    sum = 0;    for(int i = 0; i < m; i++)        cin >> edge[i].u >> edge[i].v >> edge[i].val;    ans.clear();    if(kruskal()) {        cout << "kruskal path:" << endl;        for(int i = 0; i < ans.size(); i++)     cout << ans[i].u << "->" << ans[i].v << endl;        cout << "the sum is:" << endl;        cout << sum << endl;    }    else        cout << "error" << endl;    return 0;}