Kruskal算法

//核心：按边长从小到大枚举边，第一次使得1和n连通的边的长度即为答案
#include<iostream>
#include<cstring>
#include<algorithm>

using namespace std;

const int N = 100010,M = 400010;

struct Edge
{
    int a,b,c;
    bool operator<(const Edge &t) const
    {
        return c<t.c;
    }
}e[M];

int n,m;
int p[N];

int find(int x)
{
    if(p[x]!=x) p[x] = find(p[x]);
    return p[x];
}

int main()
{
    cin>>n>>m;
    for(int i = 1; i<=n; i++) p[i] = i;
    for(int i = 0; i<m; i++)
    {
        int a,b,c;
        cin>>a>>b>>c;
        e[i] = {a,b,c};
    }
    sort(e,e+m);
    for(int i = 0; i<m; i++)
    {
        int a = e[i].a,b = e[i].b;
        a = find(a),b = find(b);
        if(a!=b)
        {
            p[a] = b;
            if(find(1) == find(n))
            {
                cout<<e[i].c;
                break;
            }
        }
    }
    return 0;
}