<p>Given an integer array <code>nums</code> and two integers <code>lower</code> and <code>upper</code>, return <em>the number of range sums that lie in</em> <code>[lower, upper]</code> <em>inclusive</em>.</p>

<p>Range sum <code>S(i, j)</code> is defined as the sum of the elements in <code>nums</code> between indices <code>i</code> and <code>j</code> inclusive, where <code>i &lt;= j</code>.</p>

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

<pre>
<strong>Input:</strong> nums = [-2,5,-1], lower = -2, upper = 2
<strong>Output:</strong> 3
<strong>Explanation:</strong> The three ranges are: [0,0], [2,2], and [0,2] and their respective sums are: -2, -1, 2.
</pre>

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

<pre>
<strong>Input:</strong> nums = [0], lower = 0, upper = 0
<strong>Output:</strong> 1
</pre>

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

<ul>
	<li><code>1 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
	<li><code>-2<sup>31</sup> &lt;= nums[i] &lt;= 2<sup>31</sup> - 1</code></li>
	<li><code>-10<sup>5</sup> &lt;= lower &lt;= upper &lt;= 10<sup>5</sup></code></li>
	<li>The answer is <strong>guaranteed</strong> to fit in a <strong>32-bit</strong> integer.</li>
</ul>

class Solution {
    class FenwickTree {
        public:
            FenwickTree(int size) {
                _size = size;
                _vals = vector<int>(size + 1, 0);
            }

            void update(int x, int val) {
                for(; x <= _size; x += (x & (-x))) {
                    _vals[x] += val;
                }
            }

            int get(int x) {
                if (x == 0) return 0;
                int ans = 0;
                for (; x; x -= (x & (-x)))
                    ans += _vals[x];
                return ans;
            }

        private:
            int _size;
            vector<int> _vals;
    };

public:
    int countRangeSum(vector<int>& nums, int lower, int upper) {
        vector<long long> com {0, -lower, -upper};
        long long sum = 0;
        for (auto const &num: nums) {
            sum += num;
            com.push_back(sum);
            com.push_back(sum - lower);
            com.push_back(sum - upper);
        }

        sort(com.begin(), com.end());
        int n = com.size();
        FenwickTree *tree = new FenwickTree(n);

        
        int k = lower_bound(com.begin(), com.end(), 0) - com.begin() + 1;
        tree->update(k, 1);

        int ret = 0;
        sum = 0;
        for (auto const& num: nums) {
            sum += num;

            int k1 = lower_bound(com.begin(), com.end(), sum - lower) - com.begin() + 1;
            int k2 = lower_bound(com.begin(), com.end(), sum - upper) - com.begin() + 1;

            ret = ret + tree->get(k1) - tree->get(k2 - 1);

            int k = lower_bound(com.begin(), com.end(), sum) - com.begin() + 1;
            tree->update(k, 1);
        }

        return ret;
    }
};
97733