feat: solve No.1630

Author: BaffinLee

1601-1700/1630. Arithmetic Subarrays.md

@@ -0,0 +1,108 @@
+# 1630. Arithmetic Subarrays
+
+- Difficulty: Medium.
+- Related Topics: Array, Sorting.
+- Similar Questions: Arithmetic Slices, Can Make Arithmetic Progression From Sequence.
+
+## Problem
+
+A sequence of numbers is called **arithmetic** if it consists of at least two elements, and the difference between every two consecutive elements is the same. More formally, a sequence `s` is arithmetic if and only if `s[i+1] - s[i] == s[1] - s[0] `for all valid `i`.
+
+For example, these are **arithmetic** sequences:
+
+```
+1, 3, 5, 7, 9
+7, 7, 7, 7
+3, -1, -5, -9
+```
+
+The following sequence is not **arithmetic**:
+
+```
+1, 1, 2, 5, 7
+```
+
+You are given an array of `n` integers, `nums`, and two arrays of `m` integers each, `l` and `r`, representing the `m` range queries, where the `ith` query is the range `[l[i], r[i]]`. All the arrays are **0-indexed**.
+
+Return **a list of **`boolean` **elements** `answer`**, where** `answer[i]` **is** `true` **if the subarray** `nums[l[i]], nums[l[i]+1], ... , nums[r[i]]`** can be **rearranged** to form an **arithmetic** sequence, and** `false` **otherwise.**
+
+ 
+Example 1:
+
+```
+Input: nums = [4,6,5,9,3,7], l = [0,0,2], r = [2,3,5]
+Output: [true,false,true]
+Explanation:
+In the 0th query, the subarray is [4,6,5]. This can be rearranged as [6,5,4], which is an arithmetic sequence.
+In the 1st query, the subarray is [4,6,5,9]. This cannot be rearranged as an arithmetic sequence.
+In the 2nd query, the subarray is [5,9,3,7]. This can be rearranged as [3,5,7,9], which is an arithmetic sequence.
+```
+
+Example 2:
+
+```
+Input: nums = [-12,-9,-3,-12,-6,15,20,-25,-20,-15,-10], l = [0,1,6,4,8,7], r = [4,4,9,7,9,10]
+Output: [false,true,false,false,true,true]
+```
+
+ 
+**Constraints:**
+
+
+	
+- `n == nums.length`
+	
+- `m == l.length`
+	
+- `m == r.length`
+	
+- `2 <= n <= 500`
+	
+- `1 <= m <= 500`
+	
+- `0 <= l[i] < r[i] < n`
+	
+- `-105 <= nums[i] <= 105`
+
+
+
+## Solution
+
+```javascript
+/**
+ * @param {number[]} nums
+ * @param {number[]} l
+ * @param {number[]} r
+ * @return {boolean[]}
+ */
+var checkArithmeticSubarrays = function(nums, l, r) {
+    return l.map((_, i) => check(nums, l[i], r[i]));
+};
+
+var check = function(nums, l, r) {
+    var map = {};
+    var min = Number.MAX_SAFE_INTEGER;
+    var max = Number.MIN_SAFE_INTEGER;
+    for (var i = l; i <= r; i++) {
+        min = Math.min(min, nums[i]);
+        max = Math.max(max, nums[i]);
+        map[nums[i]] = true;
+    }
+    var diff = (max - min) / (r - l);
+    for (var num = min; num < max; num += diff) {
+        if (map[num] === undefined) {
+            return false;
+        }
+    }
+    return true;
+};
+```
+
+**Explain:**
+
+nope.
+
+**Complexity:**
+
+* Time complexity : O(n * m).
+* Space complexity : O(n).