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| #include <iostream>
#include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>
using namespace std;
typedef long long ll;
const int N = 20010;
const int M = 200010;
int n, m;
int w[M];
int to[M], nxt[M], fir[N], edge_num, len[M];
void addEdge(int u, int v, int w) {
to[++edge_num] = v;
len[edge_num] = w;
nxt[edge_num] = fir[u];
fir[u] = edge_num;
}
int W;
int col[N];
bool dfs(int u) {
for(int i = fir[u]; i; i = nxt[i]) {
if(len[i] <= W) continue;
int v = to[i];
if(col[u] == col[v]) {
return false;
}
if(!col[v]) {
col[v] = 3 - col[u];
if(!dfs(v)) {
return false;
}
}
}
return true;
}
bool check() {
for(int i = 1; i <= n; i++) {
if(!col[i]) {
col[i] = 1;
if(!dfs(i)) return false;
}
}
return true;
}
int main() {
cin >> n >> m;
for(int i = 1; i <= m; i++){
int a, b, c;
scanf("%d%d%d", &a, &b, &c);
addEdge(a, b, c);
addEdge(b, a, c);
w[i] = c;
}
sort(w + 1, w + m + 1);
int l = 1, r = m;
int ans = 0;
while(l < r) {
int mid = l + r >> 1;
W = w[mid];
memset(col, 0, sizeof(col));
if(check()) ans = w[mid], r = mid;
else l = mid + 1;
}
if(l == 1 && r < l) cout << 0 << endl;
else printf("%d\n", ans);
return 0;
}
|
