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| #include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef pair<int, int> pii;
#define rep(i, a, n) for (int i = a; i < n; ++i)
#define per(i, a, n) for (int i = n - 1; i >= a; --i)
#define fi first
#define pb push_back
#define mp make_pair
#define EPS 1e-8
#define INF 0x3f3f3f3f3f
#define endl '\n'
#define all(x) x.bgein(), x.end()
const int maxn = 2e4 + 5;
const int maxm = 2e5 + 5;
struct Edge {
int u, v, w;
Edge(int _u, int _v, int _w)
: u(_u)
, v(_v)
, w(_w)
{
}
Edge() {}
bool operator<(const Edge b) { return w > b.w; }
} p[maxm];
vector<pii> e[maxn];
int n, m, k, t, vis[maxn];
inline void init()
{
rep(i, 0, n + 1) e[i].clear();
}
bool dfs(int x, int co)
{
vis[x] = co;
rep(i, 0, e[x].size())
{
int y = e[x][i].first;
if (vis[y] == co)
return 0;
else if (!vis[y] && !dfs(y, 3 - co))
return 0;
}
return 1;
}
inline bool pd(int mid)
{
init();
memset(vis, 0, sizeof(vis));
rep(i, 0, m)
{
if (p[i].w <= mid)
break;
e[p[i].u].pb(mp(p[i].v, p[i].w));
e[p[i].v].pb(mp(p[i].u, p[i].w));
}
rep(i, 1, n + 1)
{
if (!vis[i] && !dfs(i, 1))
return 0;
}
return 1;
}
int main()
{
ios::sync_with_stdio(false);
while (cin >> n >> m) {
rep(i, 0, m)
{
cin >> p[i].u >> p[i].v >> p[i].w;
}
sort(p, p + m);
int l = 0, r = p[0].w, mid;
while (l < r) {
mid = (l + r) >> 1;
if (pd(mid))
r = mid;
else
l = mid + 1;
}
cout << l << endl;
}
}
|