Create Palindrome pairs using bitmasks.cpp

Author: nikolatechie

Palindrome pairs using bitmasks.cpp

@@ -0,0 +1,60 @@
+// Finding pairs of strings such that they can form a palindrome after concatenation and ordering
+#include <bits/stdc++.h>
+#include <ext/rope>
+using namespace std;
+using namespace __gnu_cxx;
+
+using ci = const int;
+using ld = long double;
+using llint = long long;
+using ullint = unsigned long long;
+using pii = pair <int,int>;
+using pcc = pair <char,char>;
+using pss = pair <string,string>;
+using vi = vector <int>;
+using vb = vector <bool>;
+using vii = vi::iterator;
+
+#define INF (1<<30)
+#define MOD 1000000007
+#define mt make_tuple
+#define all(c) c.begin(), c.end()
+#define ms(name,val) memset(name, val, sizeof name)
+#define np nullptr
+
+
+int main()
+{
+    ios_base::sync_with_stdio(0);
+    //cin.tie(0);
+
+    int n;
+    cin >> n;
+    map <llint,int> cnt;
+    llint ans = 0;
+
+    for (int t1 = 0; t1 < n; ++t1)
+    {
+        llint mask = 0;
+        string s;
+        cin >> s;
+
+        for (char c: s)
+            mask ^= (1LL<<(c-'a'));
+
+        ans += cnt[mask];
+
+        for (int t2 = 0; t2 < 63; ++t2)
+        {
+            llint tmp = mask^(1LL<<t2);
+            ans += cnt[tmp];
+        }
+
+        ++cnt[mask];
+    }
+
+    cout << ans << '\n';
+
+
+    return 0;
+}