Solution.cpp

class Node {
public:
    Node* left;
    Node* right;
    int l;
    int r;
    int mid;
    int v;
    int add;

    Node(int l, int r) {
        this->l = l;
        this->r = r;
        this->mid = (l + r) >> 1;
        this->left = this->right = nullptr;
        v = add = 0;
    }
};

class SegmentTree {
private:
    Node* root;

public:
    SegmentTree() {
        root = new Node(1, 1e9 + 1);
    }

    void modify(int l, int r, int v) {
        modify(l, r, v, root);
    }

    void modify(int l, int r, int v, Node* node) {
        if (l > r) {
            return;
        }
        if (node->l >= l && node->r <= r) {
            node->v += v;
            node->add += v;
            return;
        }
        pushdown(node);
        if (l <= node->mid) {
            modify(l, r, v, node->left);
        }
        if (r > node->mid) {
            modify(l, r, v, node->right);
        }
        pushup(node);
    }

    int query(int l, int r) {
        return query(l, r, root);
    }

    int query(int l, int r, Node* node) {
        if (l > r) {
            return 0;
        }
        if (node->l >= l && node->r <= r) return node->v;
        pushdown(node);
        int v = 0;
        if (l <= node->mid) {
            v = max(v, query(l, r, node->left));
        }
        if (r > node->mid) {
            v = max(v, query(l, r, node->right));
        }
        return v;
    }

    void pushup(Node* node) {
        node->v = max(node->left->v, node->right->v);
    }

    void pushdown(Node* node) {
        if (!node->left) {
            node->left = new Node(node->l, node->mid);
        }
        if (!node->right) {
            node->right = new Node(node->mid + 1, node->r);
        }
        if (node->add) {
            Node* left = node->left;
            Node* right = node->right;
            left->v += node->add;
            right->v += node->add;
            left->add += node->add;
            right->add += node->add;
            node->add = 0;
        }
    }
};

class MyCalendarThree {
public:
    SegmentTree* tree;

    MyCalendarThree() {
        tree = new SegmentTree();
    }

    int book(int start, int end) {
        tree->modify(start + 1, end, 1);
        return tree->query(1, 1e9 + 1);
    }
};

/**
 * Your MyCalendarThree object will be instantiated and called as such:
 * MyCalendarThree* obj = new MyCalendarThree();
 * int param_1 = obj->book(start,end);
 */