查找数组中最大子数组C语言实现

      一个数组，查找这个数组中最大的一个连续子数组。比如{1, 2, 3, –11}，这个数组中最大子数组为{1, 2, 3}。

     算法复杂度： O(nlgn)

      伪代码：

      C代码：

#include <stdio.h>

typedef struct index {
	int left;
	int right;
	int sum;
} index_t;

index_t find_max_crossing_subarray(int* a, int low, int mid, int high)
{
	int left_sum = 0x80000000;
	int right_sum = 0x80000000;
	int sum = 0;
	int max_left, max_right;

	int i;

	index_t value;

	for (i = mid; i >= low; i--) {
		sum += a[i];
		if (sum > left_sum) {
			left_sum = sum;
			max_left = i;
		}
	}

	sum = 0;
	for (i = mid + 1; i <= high; i++) {
		sum += a[i];
		if (sum > right_sum) {
			right_sum = sum;
			max_right = i;
		}
	}

	value.left = max_left;
	value.right = max_right;
	value.sum = left_sum + right_sum;

	return value;
}

index_t find_maximum_subarray(int *a, int low, int high)
{
	index_t left_value, right_value, value;
	int mid;

	if (high == low) {
		value.left = low;
		value.right = high;
		value.sum = a[low];
		return value;
	} else {
		mid = (high + low)/2;
		left_value = find_maximum_subarray(a, low, mid);
		right_value = find_maximum_subarray(a, mid + 1, high);
		value = find_max_crossing_subarray(a, low, mid, high);

		if (left_value.sum >= right_value.sum && left_value.sum >= value.sum)
			return left_value;
		else if (right_value.sum >= left_value.sum && right_value.sum >= value.sum)
			return right_value;
		else 
			return value;
	}
}

int main()
{
	int a[] = {3, 8, -1, -6, 12, 34, -43, 28};

	index_t value;

	value = find_maximum_subarray(a, 0, 7);

	printf("The maximum subarray is from %d to %d, sum is %d\n", value.left, value.right, value.sum);

	return 0;
}