Update high-performance solution(cpp 4ms)

Author: zouwx2cs

solution/0090.Subsets II/Solution2.cpp

@@ -0,0 +1,64 @@
+class Solution {
+private:
+    inline vector<int> Fun(vector<int> &keys, int counts[])
+    {
+        vector<int> item ;
+        for (int i = 0; i < keys.size(); ++i)
+        {
+            for (int j = 0; j < counts[i]; ++j)
+                item.push_back(keys[i]) ;
+        }
+        return item ;
+    }
+public:
+    vector<vector<int>> subsetsWithDup(vector<int>& nums) {
+        if (nums.size() == 0)
+            return {} ;
+        vector<vector<int>> res ;
+        
+        sort(nums.begin(), nums.end()) ;
+        const int len = nums.size() ;
+        nums.push_back(nums[0] - 1) ; //哨兵
+        
+        vector<int> cnts ;
+        vector<int> keys ;
+        for (int i = 0, cnt = 1; i < len; ++i)
+        {
+            if (nums[i] != nums[i+1])
+            {
+                keys.push_back(nums[i]) ;
+                cnts.push_back(cnt) ;
+                // cout << "[" << nums[i] << "]: " << cnt << endl ;
+                cnt = 1 ;
+            }
+            else
+                ++cnt ;
+        }
+        
+        int counts[cnts.size()] = {0, } ;
+        int i ;
+        while (true)
+        {
+            res.push_back(Fun(keys, counts));
+            ++counts[0] ;
+            for (i = 0; i < cnts.size(); ++i)
+            {
+                if (counts[i] > cnts[i])
+                {
+                    if (i+1 == cnts.size())
+                    {
+                        ++i ;
+                        break ;
+                    }
+                    ++counts[i+1] ;
+                    counts[i] = 0 ;
+                }
+                else
+                    break ;
+            }
+            if (i >= cnts.size())
+                break ;
+        }
+        return res ;
+    }
+};