分治算法求解最大子序列

题目：

#include
#include
using namespace std;
int max3(int a,int b,int c)
{
	if(a& a,int left,int right)
{
	if(left==right)
    {
        if(a[left]>0)
			return a[left];
		else
			return 0;
    }

	int center=(left+right)/2;
	int maxLeftSum=maxSumRec(a,left,center);  //对左边分治
	int maxRightSum=maxSumRec(a,center+1,right);  //对右边分治

	int maxLeftBorderSum=0,leftBorderSum=0;
	for(int i=center;i>=left;i--)									//考虑“穿过中间情形”，故从中间向左边遍历
	{
		leftBorderSum+=a[i];
		if(leftBorderSum>maxLeftBorderSum)
			maxLeftBorderSum=leftBorderSum;
	}

	int maxRightBorderSum=0,rightBorderSum=0;
	for(int i=center+1;i<=right;i++)							//考虑“穿过中间情形”，故从中间向右边遍历
	{
		rightBorderSum+=a[i];
		if(rightBorderSum>maxRightBorderSum)
			maxRightBorderSum=rightBorderSum;
	}

	return max3(maxLeftSum,maxRightSum,maxLeftBorderSum+maxRightBorderSum);   //三者取最大
}

int maxSubSum3(const vector& a)
{
	return maxSumRec(a,0,a.size()-1);
}
int main()
{
	int n;
	cin>>n;
	vector v;
	for(int i=0;i>x,v.push_back(x);}
	cout<