用的Kruskal,先放代码

//#include<bits/stdc++.h>
#include<iostream>
#include<iomanip>
#include<cstdio>
#include<stack>
#include<list>
#include<map>
#include<set>
#include<cmath>
#include<cstring>
#include<queue>
#include<algorithm>
#include<vector>
#define ll long long
#define reg register int
#define gc getchar()
#define MAXN 20001//边的数量 
#define MAXM 5001 //顶点数量 

using namespace std;

int m,n;
int fth[MAXM];
ll sum;

inline ll read(void);

inline int find(int x){
	
	if(fth[x]==x) return x;
	fth[x]=find(fth[x]);
	return fth[x];
	
}

struct edge{
	int from,to,len;
}a[MAXN];

inline bool cmp( edge a , edge b );



int main(void){
	
	n=read();//节点 
	m=read();//无向边 
	for(reg i=1;i<=m;i++) {
		a[i].from = read() ;
		a[i].to = read() ;
		a[i].len = read() ;
	}
	//在这里读入所有无向边
	
	sort(a+1,a+1+m,cmp);
	//把所有边依照边长进行排序
	
	for(reg i=1;i<=n;i++) fth[i]=i;
	//并查集初始化
	int k=0;
	int from_,to_;
	for(reg i=1;i<=m;i++){
		
		from_=find(a[i].from);
		to_=find(a[i].to);
		
		if(from_!=to_){
			
			//选择这一条边 
			k++;
			fth[from_]=to_;
			sum+=a[i].len;
			if(k==n-1) break; 
			
		}
	}
	
	if(k<n-1) cout<<"orz"<<endl;
	else cout<<sum<<endl;
	
	return 0;
	
}

inline ll read(void){
	ll x=0,f=0;
   	char ch=gc;
   	while(!isdigit(ch))
    	     f|=(ch=='-'),ch=gc;
   	while(isdigit(ch))
    	     x=(x<<1)+(x<<3)+(ch^48),ch=gc;
        return f ? -x : x ;
}

inline bool cmp( edge a , edge b ){
	return a.len < b.len ;
}

8,9是WA 10是MLE

求应该怎样优化