同 AcWing 257 关押罪犯
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using p = pair<int, int>;
const int maxn(2e4 + 10);
const int maxm(2e5 + 10);
int ecnt, head[maxn];
int color[maxn]; // 0: 未染色; 1: 染白色; 2: 染黑色
struct edge {
int to, wt, nxt;
} edges[maxm];
template<typename T = int>
inline const T read()
{
T x = 0, f = 1;
char ch = getchar();
while (ch < '0' || ch > '9') {
if (ch == '-') f = -1;
ch = getchar();
}
while (ch >= '0' && ch <= '9') {
x = (x << 3) + (x << 1) + ch - '0';
ch = getchar();
}
return x * f;
}
template<typename T>
inline void write(T x, bool ln)
{
if (x < 0) {
putchar('-');
x = -x;
}
if (x > 9) write(x / 10, false);
putchar(x % 10 + '0');
if (ln) putchar(10);
}
void addEdge(int u, int v, int w)
{
edges[ecnt].to = v;
edges[ecnt].wt = w;
edges[ecnt].nxt = head[u];
head[u] = ecnt++;
}
bool dfs(int u, int c, int val)
{
color[u] = c;
for (int i = head[u]; compl i; i = edges[i].nxt) {
int v = edges[i].to, w = edges[i].wt;
if (w <= val) {
continue;
}
if (color[v] == c) {
return false;
} else if (not color[v] and not dfs(v, 3 - c, val)) {
return false;
}
}
return true;
}
bool judge(int n, int val)
{
memset(color, 0, sizeof color);
for (int i = 1; i <= n; ++i) {
if (not color[i] and not dfs(i, 1, val)) {
return false;
}
}
return true;
}
int main()
{
#ifdef ONLINE_JUDGE
#else
freopen("input.txt", "r", stdin);
#endif
ios::sync_with_stdio(false);
memset(head, -1, sizeof head);
int n = read(), m = read();
while (m--) {
int u = read(), v = read(), w = read();
addEdge(u, v, w);
addEdge(v, u, w);
}
int low = 0, high = 1e9;
while (low < high) {
int mid = (low + high) / 2;
if (judge(n, mid)) {
high = mid;
} else {
low = mid + 1;
}
}
write(low, true);
return 0;
}