20231218 Finished

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jackfiled 2023-12-18 11:18:51 +08:00
parent d0dddf4ca6
commit e27f4e6f4a
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@ -4,3 +4,4 @@ mod s0020_valid_parentheses;
mod s2697_lexicographically_smallest_palindrome;
mod s0002_add_two_numbers;
mod s0003_longest_substring_without_repeating_characters;
mod s0162_find_peak_element;

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/**
* [162] Find Peak Element
*
* A peak element is an element that is strictly greater than its neighbors.
* Given a 0-indexed integer array nums, find a peak element, and return its index. If the array contains multiple peaks, return the index to any of the peaks.
* You may imagine that nums[-1] = nums[n] = -∞. In other words, an element is always considered to be strictly greater than a neighbor that is outside the array.
* You must write an algorithm that runs in O(log n) time.
*
* <strong class="example">Example 1:
*
* Input: nums = [1,2,3,1]
* Output: 2
* Explanation: 3 is a peak element and your function should return the index number 2.
* <strong class="example">Example 2:
*
* Input: nums = [1,2,1,3,5,6,4]
* Output: 5
* Explanation: Your function can return either index number 1 where the peak element is 2, or index number 5 where the peak element is 6.
*
* Constraints:
*
* 1 <= nums.length <= 1000
* -2^31 <= nums[i] <= 2^31 - 1
* nums[i] != nums[i + 1] for all valid i.
*
*/
pub struct Solution {}
// problem: https://leetcode.cn/problems/find-peak-element/
// discuss: https://leetcode.cn/problems/find-peak-element/discuss/?currentPage=1&orderBy=most_votes&query=
// submission codes start here
impl Solution {
pub fn find_peak_element(nums: Vec<i32>) -> i32 {
if nums.len() == 1 {
0
}
let (mut left, mut right) = (0, nums.len() - 1);
let compare = |x| {
if x == 0 {
nums[0] > nums[1]
} else if x == nums.len() - 1 {
nums[x] > nums[x - 1]
} else {
nums[x - 1] < nums[x] && nums[x] > nums[x + 1]
}
};
while left <= right {
let mid = (left + right) / 2;
if compare(mid) {
return mid as i32
}
if nums[mid] < nums[mid + 1] {
left += 1;
} else {
right -= 1;
}
}
-1
}
}
// submission codes end
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test_162() {
assert_eq!(2, Solution::find_peak_element(vec![1,2,3,1]));
assert_eq!(5, Solution::find_peak_element(vec![1,2,1,3,5,6,4]));
assert_eq!(1, Solution::find_peak_element(vec![1,2]));
}
}