solved 21316

Author: atobaum

21000/21316/21316.cpp

@@ -0,0 +1,32 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+#define FOR(i, a, b) for (int i = a; i < b; i++)
+
+int main() {
+  ios::sync_with_stdio(false); cin.tie(NULL);
+  vector<int> nbd[13];
+
+  FOR(i, 0, 12){
+    int x, y;
+    cin>>x>>y;
+
+    nbd[x].push_back(y);
+    nbd[y].push_back(x);
+  }
+
+  FOR(i, 1, 13){
+    if(nbd[i].size() == 3){
+      // the sum degrees of neighborhood is 6
+      int sum = 0;
+      FOR(j, 0, 3) sum += nbd[nbd[i][j]].size();
+
+      if(sum == 6){
+        cout<<i<<"\n";
+        break;
+      }
+    }
+  }
+
+  return 0;
+}