feat: start No.1942

BaffinLee · BaffinLee · commit 615280b25dd0 · 2023-05-09T23:56:13.000+08:00
diff --git a/1901-2000/1942. The Number of the Smallest Unoccupied Chair.md b/1901-2000/1942. The Number of the Smallest Unoccupied Chair.md
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+# 1942. The Number of the Smallest Unoccupied Chair
+
+- Difficulty: Medium.
+- Related Topics: Array, Heap (Priority Queue), Ordered Set.
+- Similar Questions: .
+
+## Problem
+
+There is a party where `n` friends numbered from `0` to `n - 1` are attending. There is an **infinite** number of chairs in this party that are numbered from `0` to `infinity`. When a friend arrives at the party, they sit on the unoccupied chair with the **smallest number**.
+
+
+	
+- For example, if chairs `0`, `1`, and `5` are occupied when a friend comes, they will sit on chair number `2`.
+
+
+When a friend leaves the party, their chair becomes unoccupied at the moment they leave. If another friend arrives at that same moment, they can sit in that chair.
+
+You are given a **0-indexed** 2D integer array `times` where `times[i] = [arrivali, leavingi]`, indicating the arrival and leaving times of the `ith` friend respectively, and an integer `targetFriend`. All arrival times are **distinct**.
+
+Return** the **chair number** that the friend numbered **`targetFriend`** will sit on**.
+
+ 
+Example 1:
+
+```
+Input: times = [[1,4],[2,3],[4,6]], targetFriend = 1
+Output: 1
+Explanation: 
+- Friend 0 arrives at time 1 and sits on chair 0.
+- Friend 1 arrives at time 2 and sits on chair 1.
+- Friend 1 leaves at time 3 and chair 1 becomes empty.
+- Friend 0 leaves at time 4 and chair 0 becomes empty.
+- Friend 2 arrives at time 4 and sits on chair 0.
+Since friend 1 sat on chair 1, we return 1.
+```
+
+Example 2:
+
+```
+Input: times = [[3,10],[1,5],[2,6]], targetFriend = 0
+Output: 2
+Explanation: 
+- Friend 1 arrives at time 1 and sits on chair 0.
+- Friend 2 arrives at time 2 and sits on chair 1.
+- Friend 0 arrives at time 3 and sits on chair 2.
+- Friend 1 leaves at time 5 and chair 0 becomes empty.
+- Friend 2 leaves at time 6 and chair 1 becomes empty.
+- Friend 0 leaves at time 10 and chair 2 becomes empty.
+Since friend 0 sat on chair 2, we return 2.
+```
+
+ 
+**Constraints:**
+
+
+	
+- `n == times.length`
+	
+- `2 <= n <= 104`
+	
+- `times[i].length == 2`
+	
+- `1 <= arrivali < leavingi <= 105`
+	
+- `0 <= targetFriend <= n - 1`
+	
+- Each `arrivali` time is **distinct**.
+
+
+
+## Solution
+
+```javascript
+
+```
+
+**Explain:**
+
+nope.
+
+**Complexity:**
+
+* Time complexity : O(n).
+* Space complexity : O(n).
