<p>Given an integer array <code>nums</code>, return <code>true</code> <em>if you can partition the array into two subsets such that the sum of the elements in both subsets is equal or </em><code>false</code><em> otherwise</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [1,5,11,5]
<strong>Output:</strong> true
<strong>Explanation:</strong> The array can be partitioned as [1, 5, 5] and [11].
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [1,2,3,5]
<strong>Output:</strong> false
<strong>Explanation:</strong> The array cannot be partitioned into equal sum subsets.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 200</code></li>
	<li><code>1 &lt;= nums[i] &lt;= 100</code></li>
</ul>

class Solution {
public:
    bool canPartition(vector<int>& nums) {
        int target = 0;
        for(auto& i : nums) target += i;
        if(target % 2 == 1) return false;
        target /= 2;
        unordered_set<int> main_set;
        main_set.insert(0);
        main_set.insert(nums[0]);

        for(int i = 1; i < nums.size(); i++) {
            unordered_set<int> sub_set(main_set);  
            for(auto& it : main_set) {
                if(it + nums[i] == target) return true;
                else sub_set.insert(it + nums[i]);
            }
            main_set = move(sub_set);
        }
        return false;
    }
};
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