并查集

 

 

实现并查集：

#include <iostream>
#include <vector>

using namespace std;

class UnionFindSet {
public:
    UnionFindSet(int size) : size_(size) {
        this->size_ = size;
        this->numGroups_ = size;
        this->groupSize_ = new int[size];
        this->parent_ = new int[size];

        for (int i = 0; i < size; i++) {
            parent_[i] = i;
            groupSize_[i] = 1;
        }
    }
    ~UnionFindSet() {
        delete this->groupSize_;
        delete this->parent_;
    }
    // 查找某个节点的根节点
    int FindRoot(int x) {
        int root = x;
        while (root != parent_[root]) {
            root = parent_[root];
        }
        // 路径压缩,每个节点的根节点均为root
        while (x != root) {
            int next = parent_[x];
            parent_[x] = root;
            x = next;
        }
        return root;
    }
    // 判定两个节点是否归属同一组
    bool IsConnected(int x, int y) {
        return (FindRoot(x) == FindRoot(y));
    }
    // 获取并查集的元素个数
    int GetSize() {
        return size_;
    }
    // 获取并查集组的个数
    int GetNumGroups() {
        return numGroups_;
    }
    // 获取x所在组节点个数
    int GetGroupSize(int x) {
        int root = FindRoot(x);
        return groupSize_[root];
    }
    // 获取组的个数
    int GetNumOfGroups() {
        return numGroups_;
    }
    // 合并两个节点所在组
    void Union(int x, int y) {
        if (IsConnected(x, y)) {
            return;
        }
        int xRoot = FindRoot(x);
        int yRoot = FindRoot(y);
        if (groupSize_[xRoot] < groupSize_[yRoot]) {
            groupSize_[yRoot] += groupSize_[xRoot];
            parent_[xRoot] = yRoot;
        } else {
            groupSize_[xRoot] += groupSize_[yRoot];
            parent_[yRoot] = xRoot;
        }
        numGroups_--;
        return;
    }
private:
    int size_; // 并查集中元素个数
    int *groupSize_; // 每组元素个数
    int *parent_; // 根节点
    int numGroups_; // 并查集中组的个数
};

int main()
{
    UnionFindSet unionFind(6);
    // edges = [[1,2], [2,3], [3,4], [1,4], [1,5]]
    vector<vector<int>> edges = {{1, 2}, {2, 3}, {3, 4}, {1, 4}, {1, 5}};
    for (auto &vec : edges)
    {
        unionFind.Union(vec[0], vec[1]);
    }
    for (int i = 1; i <= 5; i++) {
        cout << i << "'s root is:= "<< unionFind.FindRoot(i) << endl;
    }

    if (unionFind.IsConnected(1, 4)) {
        cout << "Detected circle!" << endl;
    } else {
        cout << "not circle!" << endl;
    }
    cout << "1's group size is:"<< unionFind.GetGroupSize(1) << endl;
    cout << "5's group size is:"<< unionFind.GetGroupSize(5) << endl;
    cout << "group size is:"<< unionFind.GetNumGroups() << endl; // group1:(1, 2, 3, 4, 5),group2:(0)
    system("pause");
    return 0;
}