https://leetcode.cn/problems/B1IidL https://leetcode.cn/problems/number-of-subarrays-with-lcm-equal-to-k https://leetcode.cn/problems/peak-index-in-a-mountain-array

Author: masx200

B1IidL/index.ts

@@ -0,0 +1,3 @@
+import peakIndexInMountainArray from "../peak-index-in-a-mountain-array/index.ts";
+
+export default peakIndexInMountainArray;

README.md

@@ -45,6 +45,12 @@ Step 2. Add the dependency
 
 <summary>展开查看</summary>
 
+https://leetcode.cn/problems/B1IidL
+
+https://leetcode.cn/problems/number-of-subarrays-with-lcm-equal-to-k
+
+https://leetcode.cn/problems/peak-index-in-a-mountain-array
+
 https://leetcode.cn/problems/convert-the-temperature
 
 https://leetcode.cn/problems/split-message-based-on-limit

number-of-subarrays-with-lcm-equal-to-k/index.ts

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+export default function subarrayLCM(nums: number[], k: number): number {
+    let cnt = 0;
+    const len = nums.length;
+
+    for (let i = 0; i < len; i++) {
+        if (k % nums[i]) continue;
+        let lcm = nums[i];
+        for (let j = i; j < len; j++) {
+            if (k % nums[j]) break;
+            lcm = getLCM(lcm, nums[j]);
+
+            if (lcm === k) cnt += 1;
+        }
+    }
+
+    return cnt;
+}
+
+function getGCD<T extends number | bigint>(a: T, b: T): T {
+    if (b == 0) return a;
+    return getGCD(b, (a % b) as T) as T;
+}
+
+function getLCM<T extends number | bigint>(a: T, b: T): T {
+    return ((a * b) / getGCD(a, b)) as T;
+}
+export { getGCD, getLCM };

peak-index-in-a-mountain-array/index.ts

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+export default function peakIndexInMountainArray(arr: number[]): number {
+    let left = 0;
+    let right = arr.length - 1;
+
+    // 可以看做寻找 arr[i + 1] 小于 arr[i] 区间内的左边界，也就是第一个 arr[i + 1] 小于 arr[i] 的索引
+    while (left <= right) {
+        const mid = left + ((right - left) >> 1);
+
+        if (arr[mid] === arr[mid + 1]) {
+            right = mid - 1;
+        } else if (arr[mid] < arr[mid + 1]) {
+            left = mid + 1;
+        } else if (arr[mid] > arr[mid + 1]) {
+            right = mid - 1;
+        }
+    }
+
+    // 题目数据保证 arr 是一个山脉数组，直接返回 left
+    return left;
+}