729.my-calendar-i.cpp

/*
 * @lc app=leetcode id=729 lang=cpp
 *
 * [729] My Calendar I
 *
 * https://leetcode.com/problems/my-calendar-i/description/
 *
 * algorithms
 * Medium (45.95%)
 * Total Accepted:    30.2K
 * Total Submissions: 64.3K
 * Testcase Example:  '["MyCalendar","book","book","book"]\n[[],[10,20],[15,25],[20,30]]'
 *
 * Implement a MyCalendar class to store your events. A new event can be added
 * if adding the event will not cause a double booking.
 * 
 * Your class will have the method, book(int start, int end). Formally, this
 * represents a booking on the half open interval [start, end), the range of
 * real numbers x such that start <= x < end.
 * 
 * A double booking happens when two events have some non-empty intersection
 * (ie., there is some time that is common to both events.)
 * 
 * For each call to the method MyCalendar.book, return true if the event can be
 * added to the calendar successfully without causing a double booking.
 * Otherwise, return false and do not add the event to the calendar.
 * Your class will be called like this: MyCalendar cal = new MyCalendar();
 * MyCalendar.book(start, end)
 * 
 * Example 1:
 * 
 * 
 * MyCalendar();
 * MyCalendar.book(10, 20); // returns true
 * MyCalendar.book(15, 25); // returns false
 * MyCalendar.book(20, 30); // returns true
 * Explanation: 
 * The first event can be booked.  The second can't because time 15 is already
 * booked by another event.
 * The third event can be booked, as the first event takes every time less than
 * 20, but not including 20.
 * 
 * 
 * 
 * 
 * Note:
 * 
 * 
 * The number of calls to MyCalendar.book per test case will be at most
 * 1000.
 * In calls to MyCalendar.book(start, end), start and end are integers in the
 * range [0, 10^9].
 * 
 * 
 * 
 * 
 */
class MyCalendar {
public:
    struct Node{
        int start = -1;
        int end = -1;
        Node* next;
        Node(int x, int y): start(x), end(y), next(NULL){};
    };
    Node* head;
    MyCalendar() {
        head = new Node(-1, -1);
    }
    
    bool book(int start, int end) {
        Node* cur = head;
        Node* prev = head;
        if(cur->next == NULL){
            cur->next = new Node(start, end);
            return true;
        }
        cur = cur->next;
        while(cur != NULL){
            if(cur->end <= start){
                if(cur->next == NULL){
                    cur->next = new Node(start, end);
                    return true;
                }
                prev = cur;
                cur = cur->next;
            }else if(end <= cur->start){
                Node* temp = new Node(start, end);
                temp->next = cur;
                prev->next = temp;
                return true;
            }else{
                return false;
            }
        }
        return false;
    }
};

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