题目描述
如何得到一个数据流中的中位数?如果从数据流中读出奇数个数值,那么中位数就是所有数值排序之后位于中间的数值。如果从数据流中读出偶数个数值,那么中位数就是所有数值排序之后中间两个数的平均值。
class Solution {
public:
//思路就是把数据分半,前半部分用最大堆,后半部分用最小堆
//然后中位数,就是堆顶数中做运算
void Insert(int num)
{
if (MaxHeap.empty())
pushMax(num);
else
{
int d = MaxHeap.size() - MinHeap.size();
if (num <= MaxHeap[0])
{
pushMax(num);
if (d == 1)
{
int x = MaxHeap[0];
popMax();
pushMin(x);
}
}
else
{
pushMin(num);
if (d == -1)
{
int x = MinHeap[0];
popMin();
pushMax(x);
}
}
}
}
double GetMedian()
{
if (MaxHeap.size() == 0 && MinHeap.size() == 0)
return 0;
int d = MaxHeap.size() - MinHeap.size();
double ans = 0;
if (d == 0)
ans = (MaxHeap[0] + MinHeap[0])/2.0;
else if (d == 1)
ans = MaxHeap[0];
else
ans = MinHeap[0];
return ans;
}
private:
vector<int> MaxHeap, MinHeap;
void pushMax(int num)
{
MaxHeap.push_back(num);
push_heap(MaxHeap.begin(), MaxHeap.end(), less<int>());
}
void popMax()
{
pop_heap(MaxHeap.begin(), MaxHeap.end(), less<int>());
MaxHeap.pop_back();
}
void pushMin(int num)
{
MinHeap.push_back(num);
push_heap(MinHeap.begin(), MinHeap.end(), greater<int>());
}
void popMin()
{
pop_heap(MinHeap.begin(), MinHeap.end(), greater<int>());
MinHeap.pop_back();
}
};