|
| 1 | +# [1656. Design an Ordered Stream](https://leetcode.com/problems/design-an-ordered-stream/) |
| 2 | + |
| 3 | +## 题目 |
| 4 | + |
| 5 | +There is a stream of `n` `(id, value)` pairs arriving in an **arbitrary** order, where `id` is an integer between `1` and `n` and `value` is a string. No two pairs have the same `id`. |
| 6 | + |
| 7 | +Design a stream that returns the values in **increasing order of their IDs** by returning a **chunk** (list) of values after each insertion. The concatenation of all the **chunks** should result in a list of the sorted values. |
| 8 | + |
| 9 | +Implement the `OrderedStream` class: |
| 10 | + |
| 11 | +- `OrderedStream(int n)` Constructs the stream to take `n` values. |
| 12 | +- `String[] insert(int id, String value)` Inserts the pair `(id, value)` into the stream, then returns the **largest possible chunk** of currently inserted values that appear next in the order. |
| 13 | + |
| 14 | +**Example:** |
| 15 | + |
| 16 | + |
| 17 | + |
| 18 | +``` |
| 19 | +Input |
| 20 | +["OrderedStream", "insert", "insert", "insert", "insert", "insert"] |
| 21 | +[[5], [3, "ccccc"], [1, "aaaaa"], [2, "bbbbb"], [5, "eeeee"], [4, "ddddd"]] |
| 22 | +Output |
| 23 | +[null, [], ["aaaaa"], ["bbbbb", "ccccc"], [], ["ddddd", "eeeee"]] |
| 24 | +
|
| 25 | +Explanation |
| 26 | +// Note that the values ordered by ID is ["aaaaa", "bbbbb", "ccccc", "ddddd", "eeeee"]. |
| 27 | +OrderedStream os = new OrderedStream(5); |
| 28 | +os.insert(3, "ccccc"); // Inserts (3, "ccccc"), returns []. |
| 29 | +os.insert(1, "aaaaa"); // Inserts (1, "aaaaa"), returns ["aaaaa"]. |
| 30 | +os.insert(2, "bbbbb"); // Inserts (2, "bbbbb"), returns ["bbbbb", "ccccc"]. |
| 31 | +os.insert(5, "eeeee"); // Inserts (5, "eeeee"), returns []. |
| 32 | +os.insert(4, "ddddd"); // Inserts (4, "ddddd"), returns ["ddddd", "eeeee"]. |
| 33 | +// Concatentating all the chunks returned: |
| 34 | +// [] + ["aaaaa"] + ["bbbbb", "ccccc"] + [] + ["ddddd", "eeeee"] = ["aaaaa", "bbbbb", "ccccc", "ddddd", "eeeee"] |
| 35 | +// The resulting order is the same as the order above. |
| 36 | +
|
| 37 | +``` |
| 38 | + |
| 39 | +**Constraints:** |
| 40 | + |
| 41 | +- `1 <= n <= 1000` |
| 42 | +- `1 <= id <= n` |
| 43 | +- `value.length == 5` |
| 44 | +- `value` consists only of lowercase letters. |
| 45 | +- Each call to `insert` will have a unique `id.` |
| 46 | +- Exactly `n` calls will be made to `insert`. |
| 47 | + |
| 48 | +## 题目大意 |
| 49 | + |
| 50 | +有 n 个 (id, value) 对,其中 id 是 1 到 n 之间的一个整数,value 是一个字符串。不存在 id 相同的两个 (id, value) 对。 |
| 51 | + |
| 52 | +设计一个流,以 任意 顺序获取 n 个 (id, value) 对,并在多次调用时 按 id 递增的顺序 返回一些值。 |
| 53 | + |
| 54 | +实现 OrderedStream 类: |
| 55 | + |
| 56 | +- OrderedStream(int n) 构造一个能接收 n 个值的流,并将当前指针 ptr 设为 1 。 |
| 57 | +- String[] insert(int id, String value) 向流中存储新的 (id, value) 对。存储后: |
| 58 | +如果流存储有 id = ptr 的 (id, value) 对,则找出从 id = ptr 开始的 最长 id 连续递增序列 ,并 按顺序 返回与这些 id 关联的值的列表。然后,将 ptr 更新为最后那个 id + 1 。 |
| 59 | +否则,返回一个空列表。 |
| 60 | + |
| 61 | +## 解题思路 |
| 62 | + |
| 63 | +- 设计一个具有插入操作的 Ordered Stream。insert 操作先在指定位置插入 value,然后返回当前指针 ptr 到最近一个空位置的最长连续递增字符串。如果字符串不为空,ptr 移动到非空 value 的后一个下标位置处。 |
| 64 | +- 简单题。按照题目描述模拟即可。注意控制好 ptr 的位置。 |
| 65 | + |
| 66 | +## 代码 |
| 67 | + |
| 68 | +```go |
| 69 | +package leetcode |
| 70 | + |
| 71 | +type OrderedStream struct { |
| 72 | + ptr int |
| 73 | + stream []string |
| 74 | +} |
| 75 | + |
| 76 | +func Constructor(n int) OrderedStream { |
| 77 | + ptr, stream := 1, make([]string, n+1) |
| 78 | + return OrderedStream{ptr: ptr, stream: stream} |
| 79 | +} |
| 80 | + |
| 81 | +func (this *OrderedStream) Insert(id int, value string) []string { |
| 82 | + this.stream[id] = value |
| 83 | + res := []string{} |
| 84 | + if this.ptr == id || this.stream[this.ptr] != "" { |
| 85 | + res = append(res, this.stream[this.ptr]) |
| 86 | + for i := id + 1; i < len(this.stream); i++ { |
| 87 | + if this.stream[i] != "" { |
| 88 | + res = append(res, this.stream[i]) |
| 89 | + } else { |
| 90 | + this.ptr = i |
| 91 | + return res |
| 92 | + } |
| 93 | + } |
| 94 | + } |
| 95 | + if len(res) > 0 { |
| 96 | + return res |
| 97 | + } |
| 98 | + return []string{} |
| 99 | +} |
| 100 | + |
| 101 | +/** |
| 102 | + * Your OrderedStream object will be instantiated and called as such: |
| 103 | + * obj := Constructor(n); |
| 104 | + * param_1 := obj.Insert(id,value); |
| 105 | + */ |
| 106 | +``` |
0 commit comments