C语言实现经典数据结构线段树

线段树的表示如下，图中树的值表示区间值得和,线段树的表示和堆的表示方法相同。

代码

#include <stdio.h>
#define MAX_LEN 1000

void build_tree(int arr[], int tree[], int node, int start, int end) {

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

	int mid = start + (end - start) / 2;
	int left_node = node * 2 + 1;
	int right_node = node * 2 + 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;
		return;
	}
	int mid = start + (end - start) / 2;
	int left_node = node * 2 + 1;
	int right_node = node * 2 + 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];
	int mid = start + (end - start) / 2;
	int left_node = node * 2 + 1;
	int right_node = node * 2 + 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, size - 1);
	for (int i = 0; i < 15; i++)
		printf("tree[%d]=%d\n", i, tree[i]);
	printf("\n");
	update_tree(arr, tree, 0, 0, size - 1, 4, 6);
	for (int i = 0; i < 15; i++)
		printf("tree[%d]=%d\n", i, tree[i]);
	int s = query_tree(arr, tree, 0, 0, size - 1, 2, 5);
	printf("%d\n", s);

	return 0;
}