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| #include<bits/stdc++.h>
#define RG register
#define file(x) freopen(#x".in", "r", stdin);freopen(#x".out", "w", stdout);
#define for_edge(i, x) for(RG int i=head[x];i;i=e[i].next)
#define clear(x, y) memset(x, y, sizeof(x));
using namespace std;
template<typename T>
inline T read()
{
T data=0, w=1;
char ch=getchar();
while(ch!='-'&&(ch<'0'||ch>'9')) ch=getchar();
if(ch=='-') w=-1, ch=getchar();
while(ch>='0'&&ch<='9') data=(data<<3)+(data<<1)+(ch^48), ch=getchar();
return data*w;
}
const int maxn(100010), maxm(300010);
struct edge
{
int next, to;
long long dis;
} e[maxn << 1];
int head[maxn], e_num;
inline void add_edge(int from, int to, long long dis)
{
e[++e_num]={head[from], to, dis};
head[from]=e_num;
}
struct edge_k { int from, to; long long dis; } edg[maxm];
inline bool cmp(const edge_k &a, const edge_k &b) { return a.dis<b.dis; }
int fa[ma 大专栏 洛谷P4180【Beijing2010组队】次小生成树Treexn], n, m;
long long value; bool use[maxm];
inline int find(const int &x) { return fa[x] == x ? x : fa[x]=find(fa[x]); }
inline void mst()
{
long long ans=0;
for(RG int i=1;i<=n;i++) fa[i]=i;
for(RG int i=1;i<=m;i++)
{
int x=find(edg[i].from), y=find(edg[i].to);
if(x!=y)
{
fa[max(x, y)]=min(x, y);
ans+=edg[i].dis;
use[i]=true;
add_edge(edg[i].from, edg[i].to, edg[i].dis);
add_edge(edg[i].to, edg[i].from, edg[i].dis);
}
}
value = ans;
}
long long fst[maxn][18], sec[maxn][18], ANS=0;
int f[maxn][18], deep[maxn];
inline void dfs(int x)
{
for_edge(i, x)
{
int to=e[i].to; long long ds=e[i].dis;
if(to==f[x][0]) continue;
f[to][0]=x; fst[to][0]=sec[to][0]=ds;
deep[to]=deep[x]+1;
dfs(to);
}
}
inline void get_sec(long long &sec, long long a,
long long b, long long c,
long long d, long long _max)
{
if(a<_max) sec=a;
if(b<_max) sec=max(sec, b);
if(c<_max) sec=max(sec, c);
if(d<_max) sec=max(sec, d);
}
inline void init()
{
dfs(1);
for(RG int j=1;j<18;j++)
for(RG int i=1;i<=n;i++)
{
f[i][j]=f[f[i][j-1]][j-1];
long long f1=fst[i][j-1],
f2=fst[f[i][j-1]][j-1],
s1=sec[i][j-1],
s2=sec[f[i][j-1]][j-1];
fst[i][j]=max(f1, f2);
get_sec(sec[i][j], f1, f2, s1, s2, fst[i][j]);
}
}
inline long long query(int a, int b, long long dis)
{
if(deep[a]<deep[b]) swap(a, b);
long long fsa=-1, sca=-1, fsb=-1, scb=-1;
int d=deep[a]-deep[b];
for(RG int i=0;(1<<i)<=d;i++)
{
if((1<<i)&d)
{
long long tmp=sca;
get_sec(sca, fsa, fst[a][i], tmp, sec[a][i], max(fsa, fst[a][i]));
fsa=max(fsa, fst[a][i]);
a=f[a][i];
}
}
if(a==b)
{
long long tmp=sca;
get_sec(sca, fsa, fsb, tmp, scb, max(fsa, fsb));
if(dis==max(fsa, fsb)) return value-sca+dis;
else return value-max(fsa, fsb)+dis;
}
for(RG int i=17;~i;i--)
{
if(f[a][i]!=f[b][i])
{
long long tmp=sca;
get_sec(sca, fsa, fst[a][i], tmp, sec[a][i], max(fsa, fst[a][i]));
fsa=max(fsa, fst[a][i]);
a=f[a][i];
tmp=scb;
get_sec(scb, fsb, fst[b][i], tmp, sec[b][i], max(fsb, fst[b][i]));
fsb=max(fsb, fst[b][i]);
b=f[b][i];
}
}
long long tmp=sca;
get_sec(sca, fsa, fst[a][0], tmp, sec[a][0], max(fsa, fst[a][0]));
fsa=max(fsa, fst[a][0]);
a=f[a][0];
tmp=scb;
get_sec(scb, fsb, fst[b][0], tmp, sec[b][0], max(fsb, fst[b][0]));
fsb=max(fsb, fst[b][0]);
b=f[b][0];
tmp=sca;
get_sec(sca, fsa, fsb, tmp, scb, max(fsa, fsb));
if(dis==max(fsa, fsb)) return value-sca+dis;
else return value-max(fsa, fsb)+dis;
}
const long long I(9223372036854775807ll);
int main()
{
n=read<int>(); m=read<int>();
for(RG int i=1;i<=m;i++) edg[i].from=read<int>(), edg[i].to=read<int>(), edg[i].dis=read<long long>();
sort(edg+1, edg+m+1, cmp);
mst(); init();
ANS=I;
for(RG int i=1;i<=m;i++) if(!use[i]) ANS=min(ANS, query(edg[i].from, edg[i].to, edg[i].dis));
printf("%lldn", ANS);
return 0;
}
|
