atcoder/abc050C

Author: xirc

atcoder/abc050/C/main.cpp

@@ -0,0 +1,37 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+using ll = int64_t;
+using ff = long double;
+
+ll const MOD = 1e9 + 7;
+int N;
+vector<int> A;
+
+ll solve() {
+    sort(A.begin(), A.end());
+    if (N % 2 == 0 && A[0] == 0) return 0;
+    if (N % 2 == 1 && A[0] != 0) return 0;
+    for (int i = N % 2; i < N; i += 2) {
+        if (i > 0 && A[i] == A[i-1]) return 0;
+        if (A[i] != A[i+1]) return 0;
+    }
+    int M = N / 2;
+    ll ans = 1;
+    for (int i = 0; i < M; ++i) {
+        ans = (ans * 2) % MOD;
+    }
+    return ans;
+}
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(0); cout.tie(0);
+
+    cin >> N;
+    A.assign(N, 0);
+    for (auto &a : A) cin >> a;
+    cout << solve() << endl;
+
+    return 0;
+}