OJ-Problems-Source/HDOJ/4514_autoAC.cpp
2016-09-06 13:32:33 +08:00

65 lines
1.5 KiB
C++

#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <vector>
#pragma comment(linker, "/STACK:1024000000,1024000000")
using namespace std;
const int N = 100005;
int n, m, ans;
int set[N];
int dp[N];
struct Edge {
int v, f;
Edge() {}
Edge(int _v, int _f) : v(_v), f(_f) {}
};
vector<Edge>vt[N];
int find(int x) {
return x == set[x] ? x : x = find(set[x]);
}
void dfs(int p, int u) {
int forkmax = 0;
for (int i = 0; i < (int)vt[u].size(); ++i) {
int v = vt[u][i].v, f = vt[u][i].f;
if (v == p) continue;
dfs(u, v);
ans = max(ans, dp[v]+f+forkmax);
forkmax = max(forkmax, dp[v] + f);
}
dp[u] = forkmax;
}
void solve() {
for (int i = 1; i <= n; ++i) {
if (dp[i] == -1) dfs(0, i);
}
printf("%d\n", ans);
}
int main() {
while (scanf("%d %d", &n, &m) != EOF) {
int a, b, c, x, y;
bool loop = false;
ans = 0;
for (int i = 1; i <= n; ++i) {
dp[i] = -1;
set[i] = i;
vt[i].clear();
}
for (int i = 0; i < m; ++i) {
scanf("%d %d %d", &a, &b, &c);
if (loop) continue;
x = find(a), y = find(b);
if (x != y) set[x] = y;
else loop = true;
vt[a].push_back(Edge(b, c));
vt[b].push_back(Edge(a, c));
}
if (loop) {
puts("YES");
continue;
}
solve();
}
return 0;
}