G - Triangle

https://atcoder.jp/contests/abc258/submissions/32935224

AtCoder/ABC258/G/G.cpp

@@ -0,0 +1,40 @@
+#include <iostream>
+#include <bitset>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 3005;
+
+int n;
+long long ans;
+std::bitset<N> g[N];
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n;
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = 1; j <= n; j++) {
+            char c;
+            cin >> c;
+
+            if (c == '1') g[i][j] = g[j][i] = 1;
+        }
+    }
+
+    for (int i = 1; i <= n; i++) {
+        for (int j = i + 1; j <= n; j++) {
+            if (g[i][j]) {
+                ans += (g[i] & g[j]).count();
+            }
+        }
+    }
+
+    cout << ans / 3 << endl;
+
+    return 0;
+}