atcoder/abc071C

Author: xirc

atcoder/abc071/C/main.cpp

@@ -0,0 +1,43 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+using ll = long long;
+
+int N;
+vector<int> A;
+
+ll solve() {
+    map<int,int> mp;
+    for (auto v : A) {
+        ++mp[v];
+    }
+
+    ll ans = 0;
+    deque<int> Q;
+    for (auto e : mp) {
+        auto v = e.first, c = e.second;
+        if (c <= 1) continue;
+        if (c >= 4) {
+            ans = max(ans, ll(v) * v);
+        }
+        Q.push_back(v);
+        if (Q.size() < 2) continue;
+        if (Q.size() > 2) Q.pop_front();
+        ans = max(ans, ll(Q[0]) * Q[1]);
+    }
+    return ans;
+}
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(0); cout.tie(0);
+
+    cin >> N;
+    A.assign(N, 0);
+    for (int i = 0; i < N; ++i) {
+        cin >> A[i];
+    }
+    cout << solve() << endl;
+
+    return 0;
+}