kruskal算法的c++实现

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kruskal 算法的思想是将图中所有的顶点，都看作不同的连通分支，也就是他们每一个都是一个树。之后，从所有边中选权重最小的边，每次判断该边的两个顶点是否属于不同的连通分支，如果不属于，将此边加入，并修改两个顶点为一个连通分支 ; 若属于则继续选下一个权重最小的边进行上述判断，直到选中的边的个数等于N-1（N为顶点个数），算法结束，此时所有选中的边和所有的点为原图的最小生成树。

c++ 实现如下：

#include 
<iostream>
#include 
<algorithm>
#include 
<cstdio>
#include 
<vector>
#include 
<unordered_map>

struct edges{
edges(int s ,
int d , int w):source(s),dist(d),weight(w){}
int source;
int dist;
int weight;
};

bool comp(edges &a , edges &b){
return a.weight < b.weight;
}

int main(){

std::vector<edges> edge_array;
int graph[][6] = {
{0,1,4,0,0,0},
{1,0,1,0,4,0},
{4,1,0,3,0,0},
{0,0,3,0,4,5},
{0,4,0,4,0,0},
{0,0,0,5,0,0}
};

std::unordered_map<int,int> vTree;
for(int i =
0 ; i < 6 ; i++){
vTree.insert(std::make_pair(i,i));
}

for(int i =
0 ; i < 6 ; i++){
for(int j = i+1 ; j <
6 ; j++){
if(graph[i][j] != 
0){
edge_array.push_back(edges(i,j,graph[i][j]));
edge_array.push_back(edges(j,i,graph[i][j]));
}
}
}

std::sort(edge_array.begin(),edge_array.end(),comp);

//krusal algorithm begin
int weight_sum = 
0;
int i = 0;
for(auto iter = edge_array.begin(); iter != edge_array.end() ; iter++){
if(i >= 5){
break;
}else{
if( vTree.find(iter->source)->second == vTree.find(iter->dist)->second
 ){
continue;
}else{
i++;
weight_sum += iter->weight;
if(iter->source < iter->dist){
vTree.find(iter->dist)->second = vTree.find(iter->source)->second;
}else{
vTree.find(iter->source)->second = vTree.find(iter->dist)->second;
}
std::cout << "edge: " << iter->source <<
" -> " << iter->dist <<
" = " << iter->weight << std::endl;
}
}
}
std::cout << "the MST result is : " << weight_sum << std::endl;

return 0;
}