'commit'

TangDou/LuoGuBook/P1102_2.cpp

@@ -0,0 +1,18 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+const int N = 200010;
+typedef long long LL;
+unordered_map<int, int> _map;
+int a[N];
+int n;
+int c;
+LL ans;
+
+int main() {
+    cin >> n >> c;
+    for (int i = 1; i <= n; i++)cin >> a[i], _map[a[i]]++;
+    for (int i = 1; i <= n; i++)ans += _map[a[i] - c];
+    cout << ans << endl;
+    return 0;
+}