Kruscal algorithm implemented in C ++

 

Principle: Using the greedy algorithm. First of all edges according to weight in ascending order, each of the initial point is a tree (a tree node). After traversing the front edge of the current collector, the current edge xy, if x, y in our already in the minimum spanning tree, then skip this edge.

If the x, y does not have at least a minimum spanning tree in our, while adding the minimum spanning tree, and the tree that contains x and y are merged into a tree comprising a tree. (And using the combined set difference operation is completed)

Note: The code does not verify the correctness!

//Kruscal算法  2020年3月29日 21:41:19

//----------------------------------

vector<int> father; //并差集

void merge(int x,int y){
    int x_father=get_father(x),y_father=get_father(y);
    father[x]=y_father;
}

int get_father(int x){
    if(father[x]!=x){
        return father[x]=get_father(father[x]);
    }
    return x;
}
//-----------------------------------
struct Edge      // the right side 
{
     int Point1;
     int Point2;
     int Weigh; 
    Edge ( int X, int Y, int Z): Point1 (X), Point2 (Y), Weigh (Z) {} 
}; 

// - ---------------------------------- 

// find the right edge weighted undirected graph and MST 
int kruscal ( ) {
     int points; // points: points 
    COUT << " number of input points: " << endl; 
    CIN >> points; 
    father.resize (points); 
    for ( int= I 0 ; I <Points; ++ I) { 
        Father [I] = I; 
    } 
    Vector <Edge> Edges;     // Edges: set the right side of the 
    int R & lt, S, T;
     the while (R & lt CIN >>> > S >> T) { 
        edges.emplace_back (R & lt, S, T); 
    } 
    Sort (edges.begin (), edges.end (), [] ( const Edge A &, const Edge & B) { return a.weigh < b.weigh;});    // in accordance with small to large weight 
    int RES;     // right and MST 
    int edge_cnt = 0 ;      // have chosen the number of sides 
    for (const Auto & Edge: Edges) {
         int P1 = edge.point1, P2 = edge.point2;
         IF (Father [P1] == Father [P2]) { // P1, P2 has joined the MST 
            Continue ; 
        } 
        RES + = Edge. Weigh; // this is added with MST 
        ++ edge_cnt; 
        merge (P1, P2); // merge the two points 
        IF (edge_cnt> = points- . 1 ) { // edge number is -1 point, completed the construction of the MST 
            BREAK ; 
        } 
    } 
    return RES; 
}