diff --git a/25/12/comp/21q1.cpp b/25/12/comp/21q1.cpp
new file mode 100644
index 0000000..1959301
--- /dev/null
+++ b/25/12/comp/21q1.cpp
@@ -0,0 +1,10 @@
+#include <string>
+
+class Solution {
+public:
+    int mirrorDistance(int n) {
+        std::string s = std::to_string(n);
+        std::reverse(s.begin(),s.end());
+        return std::abs(n - std::stoi(s));
+    }
+};
\ No newline at end of file
diff --git a/25/12/comp/21q2.cpp b/25/12/comp/21q2.cpp
new file mode 100644
index 0000000..4b1c7fb
--- /dev/null
+++ b/25/12/comp/21q2.cpp
@@ -0,0 +1,20 @@
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+class Solution {
+public:
+  long long minCost(std::string s, std::vector<int> &cost) {
+    std::unordered_map<char, long long> m;
+    int n = cost.size();
+    long long sum = 0, ans = LLONG_MAX;
+    for (int i = 0; i < n; i++) {
+      m[s[i]] += cost[i];
+      sum += cost[i];
+    }
+    for (auto [k, v] : m) {
+      ans = std::min(ans, sum - v);
+    }
+    return ans;
+  }
+};
\ No newline at end of file
diff --git a/25/12/comp/21q3.cpp b/25/12/comp/21q3.cpp
new file mode 100644
index 0000000..2b7e571
--- /dev/null
+++ b/25/12/comp/21q3.cpp
@@ -0,0 +1,22 @@
+#include <unordered_map>
+#include <vector>
+
+class Solution {
+public:
+    int minSwaps(std::vector<int>& nums, std::vector<int>& forbidden) {
+        std::unordered_map<int, int> m1,m2;
+        int n = nums.size();
+        for (int i = 0; i < n; i++)
+        {
+            m1[nums[i]]++;
+            m2[nums[i]]++;
+        }
+        for(auto [k,v] : m1){
+            if (v + m2[k] > n)
+            {
+                return -1;
+            }
+        }
+        // ❎未完成
+    }
+};
\ No newline at end of file