852. Peak Index in a Mountain Array Medium

1/**
2 * [852] Peak Index in a Mountain Array
3 *
4 * An array arr a mountain if the following properties hold:
5 * 
6 * 	arr.length >= 3
7 * 	There exists some i with 0 < i < arr.length - 1 such that:
8 * 	
9 * 		arr[0] < arr[1] < ... < arr[i - 1] < arr[i] 
10 * 		arr[i] > arr[i + 1] > ... > arr[arr.length - 1]
11 * 	
12 * 	
13 * 
14 * Given a mountain array arr, return the index i such that arr[0] < arr[1] < ... < arr[i - 1] < arr[i] > arr[i + 1] > ... > arr[arr.length - 1].
15 * You must solve it in O(log(arr.length)) time complexity.
16 *  
17 * Example 1:
18 * 
19 * Input: arr = [0,1,0]
20 * Output: 1
21 * 
22 * Example 2:
23 * 
24 * Input: arr = [0,2,1,0]
25 * Output: 1
26 * 
27 * Example 3:
28 * 
29 * Input: arr = [0,10,5,2]
30 * Output: 1
31 * 
32 *  
33 * Constraints:
34 * 
35 * 	3 <= arr.length <= 10^5
36 * 	0 <= arr[i] <= 10^6
37 * 	arr is guaranteed to be a mountain array.
38 * 
39 */
40pub struct Solution {}
41
42// problem: https://leetcode.com/problems/peak-index-in-a-mountain-array/
43// discuss: https://leetcode.com/problems/peak-index-in-a-mountain-array/discuss/?currentPage=1&orderBy=most_votes&query=
44
45// submission codes start here
46
47impl Solution {
48    pub fn peak_index_in_mountain_array(arr: Vec<i32>) -> i32 {
49        0
50    }
51}
52
53// submission codes end
54
55#[cfg(test)]
56mod tests {
57    use super::*;
58
59    #[test]
60    fn test_852() {
61    }
62}
63