Add a lot more of my solutions.

I don't remember which ones doesn't pass though

CSES Problem Set/Palindrome Reorder.cpp

@@ -0,0 +1,121 @@
+/* Problem URL: https://cses.fi/problemset/task/1755 */
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+#define V vector
+
+#define rmin(a, b) a = min(a, b)
+#define rmax(a, b) a = max(a, b)
+
+#define rep(i, lim) for (int i = 0; i < (lim); i++)
+#define nrep(i, s, lim) for (int i = s; i < (lim); i++)
+
+#define repv(i, v) for (auto &i : (v))
+#define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; }
+#define sortv(v) sort(v.begin(), v.end())
+#define all(v) (v).begin(), (v).end()
+
+using vi = vector<int>;
+using vvi = vector<vi>;
+using vvvi = vector<vvi>;
+using vvvvi = vector<vvvi>;
+
+using ll = long long;
+
+using vl = vector<ll>;
+using vvl = vector<vl>;
+using vvvl = vector<vvl>;
+using vvvvl = vector<vvvl>;
+
+template<class v>
+auto operator<<(ostream &os, const vector<v> &vec)->ostream& {
+    os << vec[0];
+    for (size_t i = 1; i < vec.size(); i++) {
+        os << ' ' << vec[i];
+    }
+    os << '\n';
+    return os;
+}
+
+template<class v>
+auto operator>>(istream &is, vector<v> &vec)->istream& {
+    for (auto &i : vec) {
+        is >> i;
+    }
+    return is;
+}
+
+template<class v>
+auto operator<<(ostream &os, const vector<vector<v>> &vec)->ostream& {
+    for (auto &i : vec) {
+        os << i[0];
+        for (size_t j = 1; j < i.size(); j++) {
+            os << ' ' << i[j];
+        }
+        os << '\n';
+    }
+    return os;
+}
+
+template<class v>
+auto operator>>(istream  &is, vector<vector<v>> &vec)->istream& {
+    for (auto &i : vec) {
+        for (auto &j : i) {
+            is >> j;
+        }
+    }
+    return is;
+}
+
+int main()
+{
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    string a;
+    cin >> a;
+
+    vi count(26);
+
+    repv(i, a) {
+        count[i - 'A']++;
+    }
+
+    int odds = 0;
+    int odd = -1;
+    rep(i, 26) {
+        if (count[i] & 1) {
+            odds++;
+            odd = i;
+        }
+    }
+
+    if (odds > 1) {
+        cout << "NO SOLUTION\n";
+        return 0;
+    }
+
+    if (odd != -1) {
+        count[odd]--;
+    }
+
+    rep(i, 26) {
+        rep(j, count[i] / 2) {
+            cout << (char)(i + 'A');
+        }
+    }
+
+    if (odd != -1) {
+        cout << (char)(odd + 'A');
+    }
+
+    for (int i = 25; i >= 0; i--) {
+        nrep(j, count[i] / 2, count[i]) {
+            cout << (char)(i + 'A');
+        }
+    }
+    
+    cout << '\n';
+}