<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) {
        //sort from the biggest to the lowest O(nlogn)
        std::sort(nums.begin(), nums.end(), std::greater<int>());
        int sum = 0;
        sum = std::accumulate(nums.begin(), nums.end(), sum);
        if (sum % 2 == 1) {
            return false;
        }
        auto target_sum = sum/2;
        std::set<int> s;
        for (auto num : nums) {
            if (num == target_sum) {
                return true;
            }
            std::set<int> stmp = s;
            for (auto it : stmp) {
                auto tmp_calc = it + num;
                if (tmp_calc > target_sum) {
                    break;
                }

                if (tmp_calc == target_sum) {
                    return true;
                }
                s.insert(tmp_calc);
            }
            s.insert(num);
        }
        return false;
    }
};
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