线段树，（segement tree）

#include 
#include 

#define MAX_LEN 1000

void build_tree(int arr[], int tree[], int node, int start, int end)
{
	if (start == end)
	{
		tree[node] = arr[start];
	}
	else {
		int mid = (start + end) / 2;
		int left_node = 2 * node + 1;
		int right_node = 2 * node + 2;

		build_tree(arr, tree, left_node, start, mid);
		build_tree(arr, tree, right_node, mid + 1, end);
		tree[node] = tree[left_node] + tree[right_node];
	}
}


void update_tree(int arr[], int tree[], int node, int start, int end, int idx, int val) {
	if (start == end) {
		arr[idx] = val;
		tree[node] = val;
	}
	else {
		int mid = (start + end) / 2;
		int left_node = 2 * node + 1;
		int right_node = 2 * node + 2;
		if (idx >= start && idx <= mid) {
			update_tree(arr, tree, left_node, start, mid, idx, val);
		}
		else {
			update_tree(arr, tree, right_node, mid + 1, end, idx, val);
		}
		tree[node] = tree[left_node] + tree[right_node];
	}
}

int query_tree(int arr[], int tree[], int node, int start, int end, int L, int R)
{
	if (R < start || L > end)
	{
		return 0;
	}

	else if (L <= start && end <= R)
	{
		return tree[node];
	}

	else if (start == end)
	{
		return tree[node];
	}

	else {
		int mid = (start + end) / 2;
		int left_node = 2 * node + 1;
		int right_node = 2 * node + 2;
		int sum_left = query_tree(arr, tree, left_node, start, mid, L, R);
		int sum_right = query_tree(arr, tree, right_node, mid + 1, end, L, R);
		return sum_left + sum_right;
	}
}
int main()
{
	int arr[] = { 1, 3, 5, 7, 9, 11 };
	int size = 6;
	int tree[MAX_LEN] = { 0 };
	build_tree(arr, tree, 0, 0, 5);
	for (int i = 0; i < 20; i++)
	{
		printf("tree[%d] : %d \n", i, tree[i]);
	}

	return 0;
}