算法

Posted on Edited on

2023-11-10

并查集：https://blog.csdn.net/YSJ367635984/article/details/113504723

C++代码实现

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#include <iostream>
#include <vector>

class DisjointSets{
public:
    DisjointSets();
    ~DisjointSets();
    int findParentNode(int x);
    void unionSetNode(int x, int y);
private:
    std::vector<int> parent;
    int count;
};

DisjointSets::DisjointSets(): count(10) {
    for(int i = 0; i < count; ++i){
        parent[i] = i;
    }
}

DisjointSets::~DisjointSets() {}

/*
int DisjointSets::findParentNode(int x){
    if(x != parent[x]){
        findParentNode(parent[x]);
    }
    return x;
}
*/

// 优化版本的并查集，减小以后查找时间
int DisjointSets::findParentNode(int x){
    while(x != parent[x]){
        // 找一次x只是压缩一次，多找几次就会导致父节点为根节点
        parent[x] = parent[parent[x]];
        x = parent[x];
    }
    return x;
}

void DisjointSets::unionSetNode(int x, int y){
    int parent_x = findParentNode(x);
    int parent_y = findParentNode(y);

    if(parent_x == parent_y) return;

    parent[parent_y] = parent_x;
    
    --count;
}