数据流中的中位数

题目描述

#include <iostream>
#include <algorithm>
#include <functional>
#include <vector>

using namespace std;

class DynamicArray{
public:
	void Insert(int num)
	{
		if (((min.size() + max.size()) & 1) == 0)
		{
			if(max.size() > 0 && num < max[0])
			{
				max.push_back(num);
				push_heap(max.begin(),max.end(),less<int>());
				num = max[0];
				pop_heap(max.begin(), max.end(), less<int>());
				max.pop_back();
			}
			min.push_back(num);
			push_heap(min.begin(), min.end(), greater<int>());
		}
		else
		{
			if(min.size() > 0 && num > min[0])
			{
				min.push_back(num);
				push_heap(min.begin(), min.end(), greater<int>());
                num=min[0];
                pop_heap(min.begin(), min.end(), greater<int>());
                min.pop_back(); 
			}
			max.push_back(num); //把后一半找到的最大值放到前一半中
			push_heap(max.begin(), max.end(), less<int>());
		}
	}

	double GetMedian()
	{
		int size = min.size() + max.size();
		if(size == 0)
			throw exception("No numbers are availeable");

		double median = 0;
		if((size&1) != 0) {
			median = (double) min[0];	//这里一定要注意强制转换，否则就会出错
		} else {
			median = (double) (max[0] + min[0]) / 2;
		}

		return median;
	}
private:
	vector<int> min;
	vector<int> max;
};

void Test(char* testName, DynamicArray &numbers, double expected)
{
    if(testName != NULL)
        printf("%s begins: ", testName);

    if(abs(numbers.GetMedian() - expected) < 0.0000001)
        printf("Passed.\n");
    else
        printf("FAILED.\n");
}

int main(int argc, char* argv[])
{
    DynamicArray numbers;

    printf("Test1 begins: ");
    try
    {
        numbers.GetMedian();
        printf("FAILED.\n");
    }
    catch(exception e)
    {
        printf("Passed.\n");
    }

    numbers.Insert(5);
    Test("Test2", numbers, 5);

    numbers.Insert(2);
    Test("Test3", numbers, 3.5);

    numbers.Insert(3);
    Test("Test4", numbers, 3);

    numbers.Insert(4);
    Test("Test6", numbers, 3.5);

    numbers.Insert(1);
    Test("Test5", numbers, 3);

    numbers.Insert(6);
    Test("Test7", numbers, 3.5);

    numbers.Insert(7);
    Test("Test8", numbers, 4);

    numbers.Insert(0);
    Test("Test9", numbers, 3.5);

    numbers.Insert(8);
    Test("Test10", numbers, 4);

	return 0;
}