Create Palindrome Permutations II.cpp

Author: JanaSabuj

Premium/Palindrome Permutations II.cpp

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+//https://www.lintcode.com/problem/palindrome-permutation-ii/description
+class Solution {
+public:
+    /**
+     * @param s: the given string
+     * @return: all the palindromic permutations (without duplicates) of it
+     */
+     vector<char> numss;
+     vector<string> global_ans;
+     bool isOdd;
+     char oddChar;
+     
+     bool canPerm(string &str) {
+        // write your code here
+        int n = str.size();
+        map<char,int> mp;
+        
+        for(auto x: str)
+            mp[x]++;
+        
+        int odd = 0;
+        for(auto pp: mp){
+            if(pp.second & 1){
+                odd++;
+                isOdd = true;
+                oddChar = pp.first;
+            }
+            if(odd > 1)
+                return false;
+        }
+        
+        
+        for(auto pp: mp){
+            int k = pp.second;
+            k/= 2;
+            while(k--){
+                numss.push_back(pp.first);
+            }
+        }
+        
+        return true;
+    }
+    
+    void solve(int idx, vector<int>& used, vector<char>& nums, vector<char>& vec){
+        int n = nums.size();
+        // base
+        if(idx == n){
+            string str = "";
+            for(int i = 0; i < n; i++){
+                str += vec[i];
+            }
+            
+            if(isOdd)
+                str += oddChar;
+                
+            for(int i = n-1; i >= 0; i--){
+                str += vec[i];
+            }
+            global_ans.push_back(str);
+            return;
+        }
+        
+        // main
+        // _
+        for(int i = 0; i < n; i++){
+            if(used[i])
+                continue;            
+            
+            if (i > 0 and nums[i-1] == nums[i] and !used[i-1])
+                continue;
+            // dups
+            
+                used[i] = true;
+                vec.push_back(nums[i]);
+                solve(idx + 1, used, nums, vec);
+                
+                vec.pop_back();
+                used[i] = false;
+            
+        }
+    }
+    
+    vector<string> permuteUnique(vector<char>& nums) {
+        // _ _ _  
+        // ^
+        
+        int idx = 0;
+        int n = nums.size();
+        // sort(nums.begin(), nums.end());
+        
+        vector<int> used(n, 0);// bool
+        vector<char> vec;
+        solve(idx, used, nums, vec);
+        
+        return global_ans;
+    }
+    
+    vector<string> generatePalindromes(string &str) {
+        // write your code here
+        isOdd = false;
+           if(!canPerm(str))
+            return {};
+        
+        //2. generate all unique perms of first half
+        for(auto x: numss)
+            cout << x << endl;
+            
+        return permuteUnique(numss);
+    }
+};