From http://blog.chinaunix.net/uid-25304689-id-349853.html

TYVJ/1403_chinaunix.cpp

@@ -0,0 +1,74 @@
+#include <iostream>
+#include <algorithm>
+#include <cstdio>
+#include <cstring>
+#include <cstdlib>
+
+using namespace std;
+
+const int M = 100000;
+const int N = 20000;
+
+struct EDGE {
+        int a;
+        int b;
+        int v;
+} edge[M];
+
+int f[N * 2];
+
+bool Compare(const EDGE &a, const EDGE &b)
+{
+        return a.v < b.v;
+}
+
+int Find(int x)
+{
+        if (f[x] == x) {
+                return f[x];
+        } else {
+                return f[x] = Find(f[x]);
+        }
+}
+
+int main()
+{
+        int n, m;
+
+        ios::sync_with_stdio(false);
+
+        cin >> n;
+        cin >> m;
+        for (int i = 0; i < m; i++) {
+                cin >> edge[i].a;
+                cin >> edge[i].b;
+                cin >> edge[i].v;
+        }
+
+        for (int i = 0; i < n * 2; i++) {
+                f[i] = i;
+        }
+
+        sort(edge, edge + m, Compare);
+
+        for (int i = m - 1; i >= 0; i--) {
+                int x = Find(edge[i].a);
+                int y = Find(edge[i].b);
+
+                if (x == y) {
+                        cout << edge[i].v << endl;
+
+                        return 0;
+                }
+
+                int xx = Find(edge[i].a + n);
+                int yy = Find(edge[i].b + n);
+
+                f[x] = yy;
+                f[y] = xx;
+        }
+
+        cout << "0" << endl;
+
+        return 0;
+}