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class Solution {
public:
    int minSwaps(vector<int>& nums, vector<int>& forbidden) {
        int n = nums.size();
 
        // Step 1: Count conflicts and occurrences
        unordered_map<int, int> bad;   // value -> conflict count
        unordered_map<int, int> cntN;  // value -> count in nums
        unordered_map<int, int> cntF;  // value -> count in forbidden
 
        for (int i = 0; i < n; i++) {
            cntN[nums[i]]++;
            cntF[forbidden[i]]++;
 
            if (nums[i] == forbidden[i]) {
                bad[nums[i]]++;
            }
        }
 
        // Step 2: Check if solution exists
        for (auto [val, cnt] : cntN) {
            int forbSpots = cntF[val];
            int safeSpots = n - forbSpots;
 
            if (cnt > safeSpots) return -1;
        }
 
        // Step 3: Pair up conflicts using max heap
        priority_queue<int> pq;
        for (auto [val, cnt] : bad) {
            pq.push(cnt);
        }
 
        int ans = 0;
 
        // Match two groups at a time
        while (pq.size() >= 2) {
            int a = pq.top(); pq.pop();
            int b = pq.top(); pq.pop();
 
            ans++;  // One swap fixes both
 
            if (a > 1) pq.push(a - 1);
            if (b > 1) pq.push(b - 1);
        }
 
        // Handle leftover conflicts
        if (!pq.empty()) {
            ans += pq.top();
        }
 
        return ans;
    }
};

prog.cpp:3:18: error: ‘vector’ has not been declared
     int minSwaps(vector<int>& nums, vector<int>& forbidden) {
                  ^~~~~~
prog.cpp:3:24: error: expected ‘,’ or ‘...’ before ‘<’ token
     int minSwaps(vector<int>& nums, vector<int>& forbidden) {
                        ^
prog.cpp: In member function ‘int Solution::minSwaps(int)’:
prog.cpp:4:17: error: ‘nums’ was not declared in this scope
         int n = nums.size();
                 ^~~~
prog.cpp:4:17: note: suggested alternative: ‘enum’
         int n = nums.size();
                 ^~~~
                 enum
prog.cpp:7:9: error: ‘unordered_map’ was not declared in this scope
         unordered_map<int, int> bad;   // value -> conflict count
         ^~~~~~~~~~~~~
prog.cpp:7:23: error: expected primary-expression before ‘int’
         unordered_map<int, int> bad;   // value -> conflict count
                       ^~~
prog.cpp:8:23: error: expected primary-expression before ‘int’
         unordered_map<int, int> cntN;  // value -> count in nums
                       ^~~
prog.cpp:9:23: error: expected primary-expression before ‘int’
         unordered_map<int, int> cntF;  // value -> count in forbidden
                       ^~~
prog.cpp:12:13: error: ‘cntN’ was not declared in this scope
             cntN[nums[i]]++;
             ^~~~
prog.cpp:12:13: note: suggested alternative: ‘int’
             cntN[nums[i]]++;
             ^~~~
             int
prog.cpp:13:13: error: ‘cntF’ was not declared in this scope
             cntF[forbidden[i]]++;
             ^~~~
prog.cpp:13:13: note: suggested alternative: ‘int’
             cntF[forbidden[i]]++;
             ^~~~
             int
prog.cpp:13:18: error: ‘forbidden’ was not declared in this scope
             cntF[forbidden[i]]++;
                  ^~~~~~~~~
prog.cpp:16:17: error: ‘bad’ was not declared in this scope
                 bad[nums[i]]++;
                 ^~~
prog.cpp:21:19: warning: structured bindings only available with -std=c++17 or -std=gnu++17
         for (auto [val, cnt] : cntN) {
                   ^
prog.cpp:21:32: error: ‘cntN’ was not declared in this scope
         for (auto [val, cnt] : cntN) {
                                ^~~~
prog.cpp:21:32: note: suggested alternative: ‘cnt’
         for (auto [val, cnt] : cntN) {
                                ^~~~
                                cnt
prog.cpp:22:29: error: ‘cntF’ was not declared in this scope
             int forbSpots = cntF[val];
                             ^~~~
prog.cpp:22:29: note: suggested alternative: ‘int’
             int forbSpots = cntF[val];
                             ^~~~
                             int
prog.cpp:29:9: error: ‘priority_queue’ was not declared in this scope
         priority_queue<int> pq;
         ^~~~~~~~~~~~~~
prog.cpp:29:24: error: expected primary-expression before ‘int’
         priority_queue<int> pq;
                        ^~~
prog.cpp:30:19: warning: structured bindings only available with -std=c++17 or -std=gnu++17
         for (auto [val, cnt] : bad) {
                   ^
prog.cpp:30:32: error: ‘bad’ was not declared in this scope
         for (auto [val, cnt] : bad) {
                                ^~~
prog.cpp:31:13: error: ‘pq’ was not declared in this scope
             pq.push(cnt);
             ^~
prog.cpp:37:16: error: ‘pq’ was not declared in this scope
         while (pq.size() >= 2) {
                ^~
prog.cpp:48:14: error: ‘pq’ was not declared in this scope
         if (!pq.empty()) {
              ^~

Standard output is empty