「雜題亂刷」P1396

wangmarui發表於2024-06-16

二分並查集板子。

連結

直接上程式碼。

點選檢視程式碼
/*
Tips:
你陣列開小了嗎?
你MLE了嗎?
你覺得是貪心,是不是該想想dp?
一個小時沒調出來,是不是該考慮換題?
打 cf 不要用 umap!!!

記住,rating 是身外之物。

該衝正解時衝正解!

Problem:

演算法:

思路:

*/
#include<bits/stdc++.h>
using namespace std;
//#define map unordered_map
#define forl(i,a,b) for(register long long i=a;i<=b;i++)
#define forr(i,a,b) for(register long long i=a;i>=b;i--)
#define forll(i,a,b,c) for(register long long i=a;i<=b;i+=c)
#define forrr(i,a,b,c) for(register long long i=a;i>=b;i-=c)
#define lc(x) x<<1
#define rc(x) x<<1|1
#define mid ((l+r)>>1)
#define cin(x) scanf("%lld",&x)
#define cout(x) printf("%lld",x)
#define lowbit(x) (x&-x)
#define pb push_back
#define pf push_front
#define IOS ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
#define endl '\n'
#define QwQ return 0;
#define ll long long
#define ull unsigned long long
#define lcm(x,y) x/__gcd(x,y)*y
#define Sum(x,y) 1ll*(x+y)*(y-x+1)/2
#define aty cout<<"Yes\n";
#define atn cout<<"No\n";
#define cfy cout<<"YES\n";
#define cfn cout<<"NO\n";
#define xxy cout<<"yes\n";
#define xxn cout<<"no\n";
#define printcf(x) x?cout<<"YES\n":cout<<"NO\n";
#define printat(x) x?cout<<"Yes\n":cout<<"No\n";
#define printxx(x) x?cout<<"yes\n":cout<<"no\n";
ll t;
ll n,m,st,en;
ll x[100010],y[100010],z[100010];
ll id[100010];
ll find(ll x)
{
	if(x==id[x])
		return x;
	return id[x]=find(id[x]);
}
bool check(ll Mid)
{
	forl(i,1,n)
		id[i]=i;
	forl(i,1,m)
		if(z[i]<=Mid)
			id[find(x[i])]=find(y[i]);
	return find(st)==find(en);
}
void solve()
{
	cin>>n>>m>>st>>en;
	forl(i,1,m)
		cin>>x[i]>>y[i]>>z[i];
	ll L=0,R=1e5;
	while(L<R)
	{
		ll Mid=(L+R)/2;
		if(check(Mid))
			R=Mid;
		else
			L=Mid+1;
	}
	cout<<L<<endl;
}
int main()
{
	IOS;
	t=1;
 //	cin>>t;
	while(t--)
		solve();
    /******************/
	/*while(L<q[i].l) */
	/*    del(a[L++]);*/
	/*while(L>q[i].l) */
	/*    add(a[--L]);*/
	/*while(R<q[i].r) */
	/*	  add(a[++R]);*/
	/*while(R>q[i].r) */
	/*    del(a[R--]);*/
    /******************/
	QwQ;
}