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Author: assassint2017

Increasing Subsequences/Increasing_Subsequences.cpp

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+// 基本思路依然是求子集的思路
+// 引入哈希表是为了解决这种情况 [1,2,3,4,5,6,7,8,9,10,1,1,1,1,1]
+
+// Runtime: 196 ms, faster than 81.72% of C++ online submissions for Increasing Subsequences.
+// Memory Usage: 21.1 MB, less than 61.15% of C++ online submissions for Increasing Subsequences.
+
+class Solution
+{
+public:
+	vector<vector<int>> findSubsequences(vector<int>& nums)
+	{
+		vector<vector<int>> res;
+		vector<int> candidate;
+
+		helper(res, candidate, nums, 0);
+
+		return res;
+	}
+private:
+	void helper(vector<vector<int>>& res, vector<int>& candidate, vector<int>& nums, int start)
+	{
+		if (candidate.size() >= 2)
+			res.push_back(candidate);
+        
+        unordered_set<int> hashSet;
+		for (int i = start; i < nums.size(); ++i)
+		{
+			if (!candidate.empty() && candidate.back() > nums[i])
+				continue;
+            if (hashSet.find(nums[i]) == hashSet.end())
+            {
+                candidate.push_back(nums[i]);
+			    helper(res, candidate, nums, i + 1);
+			    candidate.pop_back();
+                hashSet.insert(nums[i]);
+            }
+		}
+	}
+};