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@ -4,4 +4,5 @@ mod s0020_valid_parentheses;
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mod s2697_lexicographically_smallest_palindrome;
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mod s0002_add_two_numbers;
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mod s0003_longest_substring_without_repeating_characters;
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mod s0162_find_peak_element;
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mod s2828_check_if_a_string_is_an_acronym_of_words;
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82
src/solution/s0162_find_peak_element.rs
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82
src/solution/s0162_find_peak_element.rs
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@ -0,0 +1,82 @@
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/**
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* [162] Find Peak Element
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*
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* A peak element is an element that is strictly greater than its neighbors.
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* 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.
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* 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.
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* You must write an algorithm that runs in O(log n) time.
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*
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* <strong class="example">Example 1:
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*
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* Input: nums = [1,2,3,1]
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* Output: 2
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* Explanation: 3 is a peak element and your function should return the index number 2.
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* <strong class="example">Example 2:
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*
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* Input: nums = [1,2,1,3,5,6,4]
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* Output: 5
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* 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.
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*
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* Constraints:
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*
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* 1 <= nums.length <= 1000
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* -2^31 <= nums[i] <= 2^31 - 1
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* nums[i] != nums[i + 1] for all valid i.
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*
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*/
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pub struct Solution {}
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// problem: https://leetcode.cn/problems/find-peak-element/
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// discuss: https://leetcode.cn/problems/find-peak-element/discuss/?currentPage=1&orderBy=most_votes&query=
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// submission codes start here
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impl Solution {
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pub fn find_peak_element(nums: Vec<i32>) -> i32 {
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if nums.len() == 1 {
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0
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}
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let (mut left, mut right) = (0, nums.len() - 1);
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let compare = |x| {
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if x == 0 {
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nums[0] > nums[1]
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} else if x == nums.len() - 1 {
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nums[x] > nums[x - 1]
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} else {
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nums[x - 1] < nums[x] && nums[x] > nums[x + 1]
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}
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};
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while left <= right {
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let mid = (left + right) / 2;
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if compare(mid) {
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return mid as i32
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}
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if nums[mid] < nums[mid + 1] {
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left += 1;
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} else {
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right -= 1;
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}
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}
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-1
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}
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}
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// submission codes end
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_162() {
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assert_eq!(2, Solution::find_peak_element(vec![1,2,3,1]));
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assert_eq!(5, Solution::find_peak_element(vec![1,2,1,3,5,6,4]));
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assert_eq!(1, Solution::find_peak_element(vec![1,2]));
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}
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}
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