一个简单的segment tree实现

class seg_tree_node {
public:
    int start = 0;
    int end = 0;
    int val = 0;
    seg_tree_node* left;
    seg_tree_node* right;
    seg_tree_node(int s, int e, int v, seg_tree_node* l = nullptr, seg_tree_node* r = nullptr) {
        start = s;
        end = e;
        val = v;
        left = l;
        right = r;
    }
};

class seg_tree {
public:
    seg_tree(std::vector<int>& v) {
        data.swap(v);
    }
    ~seg_tree() {
        if (root) {
            clean(root);
        }
    }

    seg_tree_node* buildTree(int start, int end) {
        if (start == end)
            return new seg_tree_node(start, end, data[start]);
        int mid = (start + end) >> 1;
        seg_tree_node* left = buildTree(start, mid);
        seg_tree_node* right = buildTree(mid + 1, end);
        return new seg_tree_node(start, end, left->val + right->val, left, right);
    }

    void updateTree(int index, int val,seg_tree_node* node) {
        if (node->start == index && node->end == index) {
            node->val = val;
            return;
        }
        int mid = (node->start + node->end) >> 1;
        if (index <= mid) {
            updateTree(index, val, node->left);
        }
        else {
            updateTree(index, val, node->right);
        }
    }

    int queryTree(int s, int e, seg_tree_node* node) {
        if (node->start == s && node->end == e) {
            return node->val;
        }
        int mid = (node->start + node->end) >> 1;
        if (mid < s) {
            return queryTree(s, e, node->right);
        }
        else if (mid >= e) {
            return queryTree(s, e, node->left);
        }
        else {
            return queryTree(s, mid, node->left) + queryTree(mid + 1, e, node->right);
        }
    }
private:
    void clean(seg_tree_node* node) {
        if (!node)
            return;
        seg_tree_node* left = node->left;
        clean(left);
        seg_tree_node* right = node->right;
        clean(right);
        delete node;
        node = nullptr;
    }
private:
    std::vector<int> data;
    seg_tree_node* root = nullptr;
};