private innerTreeNode BuiltTree(int[] nums, int startIndex, int endIndex)
{
if (startIndex > endIndex)
{
return(null);
}
else
{
innerTreeNode returnValue = new innerTreeNode();
returnValue.startIndex = startIndex;
returnValue.endIndex = endIndex;
if (startIndex == endIndex)
{
returnValue.sum = nums[startIndex];
}
else
{
int midIndex = startIndex + (endIndex - startIndex) / 2;
returnValue.LeftNode = BuiltTree(nums, startIndex, midIndex);
returnValue.RightNode = BuiltTree(nums, midIndex + 1, endIndex);
returnValue.sum = returnValue.LeftNode.sum + returnValue.RightNode.sum;
}
return(returnValue);
}
}
private void Update(innerTreeNode useNode, int useIndex, int useValue)
{
if (useNode.startIndex == useNode.endIndex)
{
useNode.sum = useValue;
}
else
{
int midIndex = useNode.startIndex + (useNode.endIndex - useNode.startIndex) / 2;
if (useIndex <= midIndex)
{
Update(useNode.LeftNode, useIndex, useValue);
}
else
{
Update(useNode.RightNode, useIndex, useValue);
}
useNode.sum = useNode.LeftNode.sum + useNode.RightNode.sum;
}
}
private int CalculateSum(innerTreeNode useNode, int i, int j)
{
if (useNode.startIndex == i && useNode.endIndex == j)
{
return(useNode.sum);
}
else
{
int midIndex = useNode.startIndex + (useNode.endIndex - useNode.startIndex) / 2;
if (j <= midIndex)
{
return(CalculateSum(useNode.LeftNode, i, j));
}
else if (i >= midIndex + 1)
{
return(CalculateSum(useNode.RightNode, i, j));
}
else
{
return(CalculateSum(useNode.RightNode, midIndex + 1, j) + CalculateSum(useNode.LeftNode, i, midIndex));
}
}
}
public NumArray(int[] nums)
{
m_rootNode = BuiltTree(nums, 0, nums.Length - 1);
}
