Add 02422.cpp

02xxx/02422.cpp

@@ -0,0 +1,37 @@
+#include <algorithm>
+#include <iostream>
+#include <unordered_set>
+#include <utility>
+using namespace std;
+
+struct pair_hash {
+  size_t operator()(const pair<int, int> &p) const {
+    return (p.first << 16) ^ p.second;
+  }
+};
+
+void solve(void) {
+  int n, m; cin >> n >> m;
+  unordered_set<pair<int, int>, pair_hash> s;
+  while (m--) {
+    int a, b; cin >> a >> b;
+    if (a > b) swap(a, b);
+    s.insert({a, b});
+  }
+
+  int ans = 0;
+  for (int i=1; i<=n-2; i++) for (int j=i+1; j<=n-1; j++) for (int k=j+1; k<=n; k++) {
+    if (s.find({i, j}) == s.end() && s.find({j, k}) == s.end() && s.find({i, k}) == s.end()) {
+      ans++;
+    }
+  }
+  cout << ans;
+}
+
+int main(void) {
+  ios::sync_with_stdio(false);
+  cin.tie(nullptr);
+
+  solve();
+  return 0;
+}