leetcode(c++)(并查集)

#include <iostream>
#include <vector>

using namespace std;

class DSU{
    public:
    vector<int>parent;
    DSU(int n)
    {
        parent = vector<int>(n);
        for(int i = 0; i< n; ++i)
        {
            parent[i] = i;
        }        
    }
    int Find(int x)
    {
        if(parent[x] != x)parent[x] = Find(parent[x]);
        return parent[x];
    }

    void Union(int x, int y)
    {
        parent[Find(x)] = Find(y);
    }
};

int findCircleNums(const vector<vector<int>>& M)
{
    DSU dsu(M.size());
    for(int i = 0; i < M.size(); ++i)
    {
        for(int j = 0; j < M[0].size(); ++j)
        {
            if(M[i][j] == 1)dsu.Union(i,j);
        }        
    }
    int res = 0;
    for(int i = 0; i < M.size(); ++i)
    {
        if(dsu.Find(i) == i) ++res;
    }
    return res;
}

vector<vector<int>>dirs{{0,1},{0,-1},{1,0},{-1,0}};

vector<int> numIslands(int m, int n, const vector<vector<int>>& position)
{
    DSU dsu(m * n);
    vector<vector<bool>>island(m,vector<bool>(n,false));
    vector<int>res;
    int cnt = 0;
    for(auto cur:position)
    {
        if(island[cur[0]][cur[1]])
        {
            res.push_back(cnt);
            continue;
        }
        island[cur[0]][cur[1]] = true;
        ++cnt;
        for(auto dir:dirs)
        {
            int x = cur[0] + dir[0],y = cur[1] + dir[1];
            if(x < 0 || x >= m || y < 0 || y >= n || island[x][y] == false)continue;
            int compoent1 = dsu.Find(cur[0] * n + cur[1]);
            int compoent2 = dsu.Find(x * n + y);
            if(compoent1 != compoent2)
            {
                dsu.Union(compoent1,compoent2);
                --cnt;
            }
        }
        res.push_back(cnt);
    }   
    return res;
}

int main()
{

    //LeetCode547
    vector<vector<int>>nums{{1,1,0},{1,1,0},{0,0,1}};
    cout << findCircleNums(nums) << endl;

    //LeetCode305
    vector<vector<int>>islands{{0,0},{0,1},{1,2},{2,1}};
    auto res = numIslands(3,3,islands);
    for(int num:res)
    {
        cout << num << " ";
    }
    cout << endl;
    return 0;
}

标签：dsu,cur,parent,int,res,查集,c++,vector,leetcode
来源： https://www.cnblogs.com/fourmi/p/16219315.html