写了很久发现对不了，然后根据讨论中的dalao指出此题应有重边

所以将标程魔改了一波

var
  n,m,i,j,k,c,d,e:longint;
  a,b:array [0..10000] of longint;
  f:array [0..2300,0..2300] of longint;
  dis:array [0..10000] of longint;
  min,sum:longint;
  used:array [0..10000] of boolean;
begin
  readln(n);
  readln(m);
  fillchar(f,sizeof(f),$7f);
  for i:=1 to m do
    begin
      readln(c,d,e);
      if (f[c,d]<>f[0,0]) then
      if (f[c,d]<e) then continue;
      f[c,d]:=e;
      f[d,c]:=e;
    end;
  fillchar(dis,sizeof(dis),$7f);
  dis[0]:=0;
  sum:=0;
  for i:=0 to n do
    begin
      min:=maxlongint;
      for j:=0 to n do
        if not used[j] and (dis[j]<min) then
          begin
            k:=j;
            min:=dis[j];
          end;
      used[k]:=true;
      sum:=sum+dis[k];
      for j:=1 to n do
        if not used[j] and (f[k,j]<dis[j]) then
          dis[j]:=f[k,j];
    end;
  writeln(sum);
end.

将其改为可以判断重边，然后就错了

下为我的程序

#include <stdio.h>
#include <algorithm>
#include <string>
#include <cstring>
#define INF 0x7f7f7f7f
#define maxn 2300001
#define max(x,y) x>y?x:y
using namespace std;
int ans=0;
int f[13000];
struct arr
{
    int x,y,w;
}a[maxn];
inline int read()
{
    int x=0,p=1; char ch=getchar();
    while (ch<'0'||ch>'9') {if (ch == '-') p=-1; ch=getchar();}
    while (ch>='0'&&ch<='9') {x=(x<<1)+(x<<3)+ch-'0'; ch=getchar();}
    return x*p;
}
int cmp(arr a,arr b)
{
    return a.w<b.w;
}
int find(int x)
{
    if (!f[x]) return x;
    f[x]=find(f[x]);
    return f[x];
}
int insert(int x,int y)
{
    if (find(x)!=find(y))
    {
        f[find(x)]=find(y);
        return 1;
    }
    return 0;
}
int main()
{
    int n=read(),m=read();

    for (int i=1;i<=m;i++)
    {
        a[i].x=read(),a[i].y=read(),a[i].w=read();
    }

    sort(a+1,a+m+1,cmp);
    for (int i=1;i<=m;i++)
    {
        if (find(a[i].x)!=find(a[i].y))
        {
            ans+=a[i].w;
            insert(a[i].x,a[i].y);
        }
    }
    printf("%d\n",ans);
}

@wzf2000 @kkksc03