atcoder/abc077C

Author: xirc

atcoder/abc077/C/main.cpp

@@ -0,0 +1,42 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+using ll = int64_t;
+using ff = long double;
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(0); cout.tie(0);
+
+    int N;
+    cin >> N;
+
+    vector<int> A(N), B(N), C(N);
+    for (auto &a : A) cin >> a;
+    for (auto &b : B) cin >> b;
+    for (auto &c : C) cin >> c;
+    sort(A.begin(), A.end());
+    sort(B.begin(), B.end());
+    sort(C.begin(), C.end());
+
+    vector<ll> DP(N, 0);
+    for (int i = 0; i < N; ++i) {
+        auto it = lower_bound(A.begin(), A.end(), B[i]);
+        int s = distance(A.begin(), it);
+        DP[i] = s;
+    }
+    for (int i = 1; i < N; ++i) {
+        DP[i] += DP[i-1];
+    }
+    ll ans = 0;
+    for (auto c : C) {
+        auto it = lower_bound(B.begin(), B.end(), c);
+        int s = distance(B.begin(), it);
+        if (s > 0) {
+            ans += DP[s-1];
+        }
+    }
+    cout << ans << endl;
+
+    return 0;
+}