// (nlgn)
public static MaximumSubarrayResult Find_Maximum_Subarray(int[] array, int low, int high)
{
var result = new MaximumSubarrayResult();
if (low == high)
{
result.max_left = low;
result.max_right = high;
result.max_sum = array[low];
return(result);
}
else
{
int mid = Convert.ToInt32(Math.Floor((low + high) / 2.0d));
var leftResult = Find_Maximum_Subarray(array, low, mid);
var rightResult = Find_Maximum_Subarray(array, mid + 1, high);
var crossResult = Find_Max_Crossing_Subarray(array, low, mid, high);
if (leftResult.max_sum >= rightResult.max_sum && leftResult.max_sum >= crossResult.max_sum)
{
return(leftResult);
}
if (rightResult.max_sum >= leftResult.max_sum && rightResult.max_sum >= crossResult.max_sum)
{
return(rightResult);
}
return(crossResult);
}
}
//暴力解法
public static MaximumSubarrayResult Find_Maximum_Subarray_Violent(int[] array, int low, int high)
{
var result = new MaximumSubarrayResult();
result.max_sum = int.MinValue;
int sum = 0;
for (int i = low; i <= high; i++)
{
for (int j = high; j >= i; j--)
{
sum = 0;
for (int k = i; k <= j; k++)
{
sum += array[k];
}
if (sum > result.max_sum)
{
result.max_sum = sum;
result.max_left = i;
result.max_right = j;
}
}
}
return(result);
}
public static MaximumSubarrayResult Find_Max_Crossing_Subarray(int[] array, int low, int mid, int high)
{
if (array == null || array.Length == 0 || low > high || low > mid || mid > high)
{
return(null);
}
var result = new MaximumSubarrayResult();
int left_sum = int.MinValue, right_sum = int.MinValue;
int sum = 0;
for (int i = mid; i >= low; i--)
{
sum += array[i];
if (sum > left_sum)
{
left_sum = sum;
result.max_left = i;
}
}
sum = 0;
for (int j = mid + 1; j <= high; j++)
{
sum += array[j];
if (sum > right_sum)
{
right_sum = sum;
result.max_right = j;
}
}
result.max_sum = left_sum + right_sum;
return(result);
}