comments	difficulty	edit_url	tags
true	中等	https://github.com/doocs/leetcode/edit/main/solution/0700-0799/0731.My%20Calendar%20II/README.md	设计 线段树 数组 二分查找 有序集合 前缀和

731. 我的日程安排表 II

English Version

题目描述

实现一个程序来存放你的日程安排。如果要添加的时间内不会导致三重预订时，则可以存储这个新的日程安排。

当三个日程安排有一些时间上的交叉时（例如三个日程安排都在同一时间内），就会产生 三重预订。

事件能够用一对整数 startTime 和 endTime 表示，在一个半开区间的时间 [startTime, endTime) 上预定。实数 x 的范围为  startTime <= x < endTime。

实现 MyCalendarTwo 类：

• MyCalendarTwo() 初始化日历对象。
• boolean book(int startTime, int endTime) 如果可以将日程安排成功添加到日历中而不会导致三重预订，返回 true。否则，返回 false 并且不要将该日程安排添加到日历中。

 

示例 1：

输入：
["MyCalendarTwo", "book", "book", "book", "book", "book", "book"]
[[], [10, 20], [50, 60], [10, 40], [5, 15], [5, 10], [25, 55]]
输出：
[null, true, true, true, false, true, true]

解释：
MyCalendarTwo myCalendarTwo = new MyCalendarTwo();
myCalendarTwo.book(10, 20); // 返回 True，能够预定该日程。
myCalendarTwo.book(50, 60); // 返回 True，能够预定该日程。
myCalendarTwo.book(10, 40); // 返回 True，该日程能够被重复预定。
myCalendarTwo.book(5, 15);  // 返回 False，该日程导致了三重预定，所以不能预定。
myCalendarTwo.book(5, 10); // 返回 True，能够预定该日程，因为它不使用已经双重预订的时间 10。
myCalendarTwo.book(25, 55); // 返回 True，能够预定该日程，因为时间段 [25, 40) 将被第三个日程重复预定，时间段 [40, 50) 将被单独预定，而时间段 [50, 55) 将被第二个日程重复预定。

 

提示：

• 0 <= start < end <= 109
• 最多调用 book 1000 次。

解法

方法一：差分

我们可以利用差分的思想，将每个时间点的预定情况记录下来，然后遍历所有时间点，统计当前时间点的预定情况，如果预定次数超过 $2$ 次，则返回 $\mathit{\text{false}}$。否则，返回 $\mathit{\text{true}}$。

时间复杂度 $O(n^2)$，空间复杂度 $O(n)$，其中 $n$ 表示日程安排的数量。

Python3

class MyCalendarTwo:

    def __init__(self):
        self.sd = SortedDict()

    def book(self, startTime: int, endTime: int) -> bool:
        self.sd[startTime] = self.sd.get(startTime, 0) + 1
        self.sd[endTime] = self.sd.get(endTime, 0) - 1
        s = 0
        for v in self.sd.values():
            s += v
            if s > 2:
                self.sd[startTime] -= 1
                self.sd[endTime] += 1
                return False
        return True


# Your MyCalendarTwo object will be instantiated and called as such:
# obj = MyCalendarTwo()
# param_1 = obj.book(startTime,endTime)

Java

class MyCalendarTwo {
    private final Map<Integer, Integer> tm = new TreeMap<>();

    public MyCalendarTwo() {
    }

    public boolean book(int startTime, int endTime) {
        tm.merge(startTime, 1, Integer::sum);
        tm.merge(endTime, -1, Integer::sum);
        int s = 0;
        for (int v : tm.values()) {
            s += v;
            if (s > 2) {
                tm.merge(startTime, -1, Integer::sum);
                tm.merge(endTime, 1, Integer::sum);
                return false;
            }
        }
        return true;
    }
}

/**
 * Your MyCalendarTwo object will be instantiated and called as such:
 * MyCalendarTwo obj = new MyCalendarTwo();
 * boolean param_1 = obj.book(startTime,endTime);
 */

C++

class MyCalendarTwo {
public:
    MyCalendarTwo() {
    }

    bool book(int startTime, int endTime) {
        ++m[startTime];
        --m[endTime];
        int s = 0;
        for (auto& [_, v] : m) {
            s += v;
            if (s > 2) {
                --m[startTime];
                ++m[endTime];
                return false;
            }
        }
        return true;
    }

private:
    map<int, int> m;
};

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

Go

type MyCalendarTwo struct {
	rbt *redblacktree.Tree[int, int]
}

func Constructor() MyCalendarTwo {
	return MyCalendarTwo{rbt: redblacktree.New[int, int]()}
}

func (this *MyCalendarTwo) Book(startTime int, endTime int) bool {
	merge := func(x, v int) {
		c, _ := this.rbt.Get(x)
		if c+v == 0 {
			this.rbt.Remove(x)
		} else {
			this.rbt.Put(x, c+v)
		}
	}

	merge(startTime, 1)
	merge(endTime, -1)

	s := 0
	for _, v := range this.rbt.Values() {
		s += v
		if s > 2 {
			merge(startTime, -1)
			merge(endTime, 1)
			return false
		}
	}
	return true
}

/**
 * Your MyCalendarTwo object will be instantiated and called as such:
 * obj := Constructor();
 * param_1 := obj.Book(startTime,endTime);
 */

TypeScript

class MyCalendarTwo {
    private tm: Record<number, number> = {};

    constructor() {}

    book(startTime: number, endTime: number): boolean {
        this.tm[startTime] = (this.tm[startTime] ?? 0) + 1;
        this.tm[endTime] = (this.tm[endTime] ?? 0) - 1;
        let s = 0;
        for (const v of Object.values(this.tm)) {
            s += v;
            if (s > 2) {
                if (--this.tm[startTime] === 0) {
                    delete this.tm[startTime];
                }
                if (++this.tm[endTime] === 0) {
                    delete this.tm[endTime];
                }
                return false;
            }
        }
        return true;
    }
}

/**
 * Your MyCalendarTwo object will be instantiated and called as such:
 * var obj = new MyCalendarTwo()
 * var param_1 = obj.book(startTime,endTime)
 */

JavaScript

var MyCalendarTwo = function () {
    this.tm = {};
};

/**
 * @param {number} startTime
 * @param {number} endTime
 * @return {boolean}
 */
MyCalendarTwo.prototype.book = function (startTime, endTime) {
    this.tm[startTime] = (this.tm[startTime] || 0) + 1;
    this.tm[endTime] = (this.tm[endTime] || 0) - 1;
    let s = 0;

    for (const v of Object.values(this.tm)) {
        s += v;
        if (s > 2) {
            if (--this.tm[startTime] === 0) {
                delete this.tm[startTime];
            }
            if (++this.tm[endTime] === 0) {
                delete this.tm[endTime];
            }
            return false;
        }
    }
    return true;
};

/**
 * Your MyCalendarTwo object will be instantiated and called as such:
 * var obj = new MyCalendarTwo()
 * var param_1 = obj.book(startTime,endTime)
 */

方法二：线段树

线段树将整个区间分割为多个不连续的子区间，子区间的数量不超过 $\log (\mathit{\text{width}})$。更新某个元素的值，只需要更新 $\log (\mathit{\text{width}})$ 个区间，并且这些区间都包含在一个包含该元素的大区间内。区间修改时，需要使用懒标记保证效率。

• 线段树的每个节点代表一个区间；
• 线段树具有唯一的根节点，代表的区间是整个统计范围，如 $[1,N]$；
• 线段树的每个叶子节点代表一个长度为 $1$ 的元区间 $[x,x]$；
• 对于每个内部节点 $[l,r]$，它的左儿子是 $[l,\mathit{\text{mid}}]$，右儿子是 $[\mathit{\text{mid}}+1,r]$, 其中 $\mathit{\text{mid}}=\lfloor (l+r)/2\rfloor$ (即向下取整)。

对于本题，线段树节点维护的信息有：

1. 区间范围内被预定的次数的最大值 $v$
2. 懒标记 $\mathit{\text{add}}$

由于时间范围为 ${10}^9$，非常大，因此我们采用动态开点。

时间复杂度 $O(n\times logn)$，空间复杂度 $O(n)$，其中 $n$ 表示日程安排的数量。

Python3

class Node:
    def __init__(self, l: int, r: int):
        self.left = None
        self.right = None
        self.l = l
        self.r = r
        self.mid = (l + r) >> 1
        self.v = 0
        self.add = 0


class SegmentTree:
    def __init__(self):
        self.root = Node(1, 10**9 + 1)

    def modify(self, l: int, r: int, v: int, node: Node = None):
        if l > r:
            return
        if node is None:
            node = self.root
        if node.l >= l and node.r <= r:
            node.v += v
            node.add += v
            return
        self.pushdown(node)
        if l <= node.mid:
            self.modify(l, r, v, node.left)
        if r > node.mid:
            self.modify(l, r, v, node.right)
        self.pushup(node)

    def query(self, l: int, r: int, node: Node = None) -> int:
        if l > r:
            return 0
        if node is None:
            node = self.root
        if node.l >= l and node.r <= r:
            return node.v
        self.pushdown(node)
        v = 0
        if l <= node.mid:
            v = max(v, self.query(l, r, node.left))
        if r > node.mid:
            v = max(v, self.query(l, r, node.right))
        return v

    def pushup(self, node: Node):
        node.v = max(node.left.v, node.right.v)

    def pushdown(self, node: Node):
        if node.left is None:
            node.left = Node(node.l, node.mid)
        if node.right is None:
            node.right = Node(node.mid + 1, node.r)
        if node.add:
            node.left.v += node.add
            node.right.v += node.add
            node.left.add += node.add
            node.right.add += node.add
            node.add = 0


class MyCalendarTwo:
    def __init__(self):
        self.tree = SegmentTree()

    def book(self, startTime: int, endTime: int) -> bool:
        if self.tree.query(startTime + 1, endTime) >= 2:
            return False
        self.tree.modify(startTime + 1, endTime, 1)
        return True


# Your MyCalendarTwo object will be instantiated and called as such:
# obj = MyCalendarTwo()
# param_1 = obj.book(startTime,endTime)

Java

class Node {
    Node left;
    Node right;
    int l;
    int r;
    int mid;
    int v;
    int add;
    public Node(int l, int r) {
        this.l = l;
        this.r = r;
        this.mid = (l + r) >> 1;
    }
}

class SegmentTree {
    private Node root = new Node(1, (int) 1e9 + 1);

    public SegmentTree() {
    }

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

    public 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);
    }

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

    public 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 = Math.max(v, query(l, r, node.left));
        }
        if (r > node.mid) {
            v = Math.max(v, query(l, r, node.right));
        }
        return v;
    }

    public void pushup(Node node) {
        node.v = Math.max(node.left.v, node.right.v);
    }

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

class MyCalendarTwo {
    private SegmentTree tree = new SegmentTree();

    public MyCalendarTwo() {
    }

    public boolean book(int startTime, int endTime) {
        if (tree.query(startTime + 1, endTime) >= 2) {
            return false;
        }
        tree.modify(startTime + 1, endTime, 1);
        return true;
    }
}

/**
 * Your MyCalendarTwo object will be instantiated and called as such:
 * MyCalendarTwo obj = new MyCalendarTwo();
 * boolean param_1 = obj.book(startTime,endTime);
 */

C++

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

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

class SegmentTree {
public:
    Node* root;

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

    void modify(int l, int r, int v, Node* node = nullptr) {
        if (l > r) {
            return;
        }
        if (node == nullptr) {
            node = root;
        }

        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, Node* node = nullptr) {
        if (l > r) {
            return 0;
        }
        if (node == nullptr) {
            node = root;
        }

        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;
    }

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

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

class MyCalendarTwo {
public:
    SegmentTree tree;

    MyCalendarTwo() {}

    bool book(int startTime, int endTime) {
        if (tree.query(startTime + 1, endTime) >= 2) {
            return false;
        }
        tree.modify(startTime + 1, endTime, 1);
        return true;
    }
};

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

Go

type node struct {
	left      *node
	right     *node
	l, mid, r int
	v, add    int
}

func newNode(l, r int) *node {
	return &node{
		l:   l,
		r:   r,
		mid: int(uint(l+r) >> 1),
	}
}

type segmentTree struct {
	root *node
}

func newSegmentTree() *segmentTree {
	return &segmentTree{
		root: newNode(1, 1e9+1),
	}
}

func (t *segmentTree) modify(l, r, v int, n *node) {
	if l > r {
		return
	}
	if n.l >= l && n.r <= r {
		n.v += v
		n.add += v
		return
	}
	t.pushdown(n)
	if l <= n.mid {
		t.modify(l, r, v, n.left)
	}
	if r > n.mid {
		t.modify(l, r, v, n.right)
	}
	t.pushup(n)
}

func (t *segmentTree) query(l, r int, n *node) int {
	if l > r {
		return 0
	}
	if n.l >= l && n.r <= r {
		return n.v
	}
	t.pushdown(n)
	v := 0
	if l <= n.mid {
		v = max(v, t.query(l, r, n.left))
	}
	if r > n.mid {
		v = max(v, t.query(l, r, n.right))
	}
	return v
}

func (t *segmentTree) pushup(n *node) {
	n.v = max(n.left.v, n.right.v)
}

func (t *segmentTree) pushdown(n *node) {
	if n.left == nil {
		n.left = newNode(n.l, n.mid)
	}
	if n.right == nil {
		n.right = newNode(n.mid+1, n.r)
	}
	if n.add != 0 {
		n.left.add += n.add
		n.right.add += n.add
		n.left.v += n.add
		n.right.v += n.add
		n.add = 0
	}
}

type MyCalendarTwo struct {
	tree *segmentTree
}

func Constructor() MyCalendarTwo {
	return MyCalendarTwo{newSegmentTree()}
}

func (this *MyCalendarTwo) Book(startTime int, endTime int) bool {
	if this.tree.query(startTime+1, endTime, this.tree.root) >= 2 {
		return false
	}
	this.tree.modify(startTime+1, endTime, 1, this.tree.root)
	return true
}

/**
 * Your MyCalendarTwo object will be instantiated and called as such:
 * obj := Constructor();
 * param_1 := obj.Book(startTime,endTime);
 */

TypeScript

class Node {
    left: Node | null = null;
    right: Node | null = null;
    l: number;
    r: number;
    mid: number;
    v: number = 0;
    add: number = 0;

    constructor(l: number, r: number) {
        this.l = l;
        this.r = r;
        this.mid = (l + r) >> 1;
    }
}

class SegmentTree {
    private root: Node = new Node(1, 1e9 + 1);

    modify(l: number, r: number, v: number, node: Node | null = this.root): void {
        if (l > r || !node) {
            return;
        }
        if (node.l >= l && node.r <= r) {
            node.v += v;
            node.add += v;
            return;
        }
        this.pushdown(node);
        if (l <= node.mid) {
            this.modify(l, r, v, node.left);
        }
        if (r > node.mid) {
            this.modify(l, r, v, node.right);
        }
        this.pushup(node);
    }

    query(l: number, r: number, node: Node | null = this.root): number {
        if (l > r || !node) {
            return 0;
        }
        if (node.l >= l && node.r <= r) {
            return node.v;
        }
        this.pushdown(node);
        let v = 0;
        if (l <= node.mid) {
            v = Math.max(v, this.query(l, r, node.left));
        }
        if (r > node.mid) {
            v = Math.max(v, this.query(l, r, node.right));
        }
        return v;
    }

    private pushup(node: Node): void {
        if (node.left && node.right) {
            node.v = Math.max(node.left.v, node.right.v);
        }
    }

    private pushdown(node: Node): void {
        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) {
            let left = node.left;
            let right = node.right;
            left.add += node.add;
            right.add += node.add;
            left.v += node.add;
            right.v += node.add;
            node.add = 0;
        }
    }
}

class MyCalendarTwo {
    private tree: SegmentTree = new SegmentTree();

    constructor() {}

    book(startTime: number, endTime: number): boolean {
        if (this.tree.query(startTime + 1, endTime) >= 2) {
            return false;
        }
        this.tree.modify(startTime + 1, endTime, 1);
        return true;
    }
}

/**
 * Your MyCalendarTwo object will be instantiated and called as such:
 * var obj = new MyCalendarTwo()
 * var param_1 = obj.book(startTime,endTime)
 */

JavaScript

class Node {
    constructor(l, r) {
        this.left = null;
        this.right = null;
        this.l = l;
        this.r = r;
        this.mid = (l + r) >> 1;
        this.v = 0;
        this.add = 0;
    }
}

class SegmentTree {
    constructor() {
        this.root = new Node(1, 1e9 + 1);
    }

    modify(l, r, v, node = this.root) {
        if (l > r || !node) {
            return;
        }
        if (node.l >= l && node.r <= r) {
            node.v += v;
            node.add += v;
            return;
        }
        this.pushdown(node);
        if (l <= node.mid) {
            this.modify(l, r, v, node.left);
        }
        if (r > node.mid) {
            this.modify(l, r, v, node.right);
        }
        this.pushup(node);
    }

    query(l, r, node = this.root) {
        if (l > r || !node) {
            return 0;
        }
        if (node.l >= l && node.r <= r) {
            return node.v;
        }
        this.pushdown(node);
        let v = 0;
        if (l <= node.mid) {
            v = Math.max(v, this.query(l, r, node.left));
        }
        if (r > node.mid) {
            v = Math.max(v, this.query(l, r, node.right));
        }
        return v;
    }

    pushup(node) {
        if (node.left && node.right) {
            node.v = Math.max(node.left.v, node.right.v);
        }
    }

    pushdown(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) {
            const left = node.left;
            const right = node.right;
            left.add += node.add;
            right.add += node.add;
            left.v += node.add;
            right.v += node.add;
            node.add = 0;
        }
    }
}

var MyCalendarTwo = function () {
    this.tree = new SegmentTree();
};

/**
 * @param {number} startTime
 * @param {number} endTime
 * @return {boolean}
 */
MyCalendarTwo.prototype.book = function (startTime, endTime) {
    if (this.tree.query(startTime + 1, endTime) >= 2) {
        return false;
    }
    this.tree.modify(startTime + 1, endTime, 1);
    return true;
};

/**
 * Your MyCalendarTwo object will be instantiated and called as such:
 * var obj = new MyCalendarTwo()
 * var param_1 = obj.book(startTime,endTime)
 */