【剑指offer】题36：数组中的逆序对

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int InversePairs_Core(vector<int>& data, vector<int>& copy, int left, int right){    if (left>=right)        return 0;    int mid = left + ((right - left) >> 1);    int leftNum = InversePairs_Core(copy, data, left, mid);    int rightNum = InversePairs_Core(copy, data, mid + 1, right);    int count(0), i(right), left_index(mid), right_index(right);    while (left_index>=left&&right_index>=mid+1)    {        if (data[left_index]>data[right_index])        {            count += right_index-mid;            if (count>1000000007)            {                count %= 1000000007;            }            copy[i--] = data[left_index--];        }        else        {            copy[i--] = data[right_index--];        }    }    while (left_index>=left)    {        copy[i--] = data[left_index--];    }    while (right_index>=mid+1)    {        copy[i--] = data[right_index--];    }    return (count + leftNum + rightNum) % 1000000007;}int InversePairs(vector<int>& data){    if (data.size() < 2)        return 0;    vector<int> copy(data);    return InversePairs_Core(data, copy, 0, data.size() - 1);}int main(){    vector<int> vec{ 7,5,6,4 };    cout<<InversePairs(vec);#ifdef debug_#else#endifreturn 0;}

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