最大子列和

最大子列和问题代码实现，实现代码为c语言，但使用了c++的I/O组件

#include <iostream>
using namespace std;

/*
	len = 8
	len / 2 = 4  
	len - len / 2 = 4
	*   *   *   *   /   *   *   *   *
	0        len/2-1  len/2        len-1
	(a + 0, 4)	        (a + 4, 4)
	
	len = 7
	len / 2 = 3
	len - len / 2 = 4
	*   *   *   /   *   *   *   *
	0     len/2-1  len/2       len-1
	(a + 0, 3)      (a + 3, 4)
*/

int MaxSubSeqSum(int a[], int len) {
	if(len > 1) {
		//将原序列划分为左右两部分
		int MaxOfLeft = MaxSubSeqSum(a, len / 2);
		int MaxOfRight = MaxSubSeqSum(a + len / 2, len - len / 2);
		int MaxOfBothSides = MaxOfLeft > MaxOfRight ? MaxOfLeft : MaxOfRight;
		
		int MaxToLeft = 0;
		int SumToLeft = 0;
		for(int i = len / 2 - 1; i >= 0; i--) {
			SumToLeft += a[i];
			if(SumToLeft > MaxToLeft) MaxToLeft = SumToLeft;
		}
		int MaxToRight = 0;
		int SumToRight = 0;
		for(int i = len / 2; i <= len - 1; i++) {
			SumToRight += a[i];
			if(SumToRight > MaxToRight) MaxToRight = SumToRight;
		}
		int MaxCross = MaxToLeft + MaxToRight;
		return MaxOfBothSides > MaxCross ? MaxOfBothSides : MaxCross;
	} else {
		return a[0] > 0 ? a[0] : 0;
	}
}

int main() {
	int n;
	int* arr;
	
	cin >> n;
	arr = new int[n];
	
	for(int i = 0; i < n; i++)
	{
		int t;
		cin >> t;
		arr[i] = t;
	}
	
	int maxSum = MaxSubSeqSum(arr, n);
	cout << maxSum;
	
	return 0;
}