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MARYBMW.cpp
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MARYBMW.cpp
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#include<bits/stdc++.h>
using namespace std;
#define vi vector<long long int>
#define set1 set<long long int>
#define pb push_back
#define pob pop_back
#define map1 map<long long int,long long int>
#define ll long long int
#define mp make_pair
#define inf 1e18+1
#define minf INT_MIN
#define setbits(x) __builtin_popcountll(x)
#define pres(x,y) fixed<<setprecision(y)<<x
#define pair1 pair<long long int,long long int>
#define mk(arr,n,type) type *arr=new type[n];
#define mod 1000000007
#define pi 3.1415926535897932384626433832
#define ins insert
#define what_is(x) cerr << #x << " is " << x << endl;
#define w(t) long long int t;cin>>t;while(t--)
struct edge
{
ll a, b, w;
};
vector<edge> v;
vector<ll> par;
ll getp(ll x) {
if (par[x] == -1) {
return x;
}
return par[x] = getp(par[x]);
}
void unite(ll x, ll y) {
x = getp(x);
y = getp(y);
par[x] = y;
}
bool comp(edge e1, edge e2) {
return e1.w > e2.w;
}
vector<vector<pair1>> g;
void solve() {
ll n, m;
cin >> n >> m;
v.clear();
g.resize(n + 1);
g.clear();
for (ll i = 1; i <= n; i++) {
g[i].clear();
}
par.assign(n + 1, -1);
for (ll i = 0; i < m; i++) {
ll x, y, z;
cin >> x >> y >> z;
v.pb({x, y, z});
}
sort(v.begin(), v.end(), comp);
for (auto x : v) {
if (getp(x.a) != getp(x.b)) {
unite(x.a, x.b);
g[x.a].pb({x.b, x.w});
g[x.b].pb({x.a, x.w});
}
}
if (getp(1) != getp(n)) {
cout << "-1" << "\n";
return;
}
queue<ll> q;
q.push(1);
vi vis(n + 1, -1);
vi p1(n + 1, -1), c1(n + 1, 0);
vector<pair1> pd;
while (!q.empty()) {
ll src = q.front();
q.pop();
vis[src] = 1;
for (auto x : g[src]) {
if (vis[x.first] == -1) {
q.push(x.first);
p1[x.first] = src;
c1[x.first] = x.second;
}
}
}
ll p = p1[n];
ll res = c1[n];
while (p != 1) {
if (res == -1) {
res = c1[p];
}
res = min(res, c1[p]);
p = p1[p];
}
cout << res << "\n";
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
#ifndef ONLINE_JUDGE
freopen("inp.txt", "r", stdin);
freopen("out.txt", "w", stdout);
#endif
w(t) {
solve();
}
return 0;
}