34. Find First and Last Position of Element in Sorted Array

Given an array of integers nums sorted in ascending order, find the starting and ending position of a given target value.

If target is not found in the array, return [-1, -1].

Follow up: Could you write an algorithm with O(log n) runtime complexity?

 

Example 1:

Input: nums = [5,7,7,8,8,10], target = 8
Output: [3,4]

Example 2:

Input: nums = [5,7,7,8,8,10], target = 6
Output: [-1,-1]

Example 3:

Input: nums = [], target = 0
Output: [-1,-1]

 

Constraints:

  • 0 <= nums.length <= 105
  • -109 <= nums[i] <= 109
  • nums is a non-decreasing array.
  • -109 <= target <= 109

Rust Solution

struct Solution;

impl Solution {
    fn search_range(nums: Vec<i32>, target: i32) -> Vec<i32> {
        let n = nums.len();
        match nums.binary_search(&target) {
            Ok(i) => {
                let mut l = i;
                let mut r = i;
                while l > 0 && nums[l - 1] == target {
                    l -= 1;
                }
                while r + 1 < n && nums[r + 1] == target {
                    r += 1;
                }
                vec![l as i32, r as i32]
            }
            Err(_) => vec![-1, -1],
        }
    }
}

#[test]
fn test() {
    let nums = vec![5, 7, 7, 8, 8, 10];
    let target = 8;
    let res = vec![3, 4];
    assert_eq!(Solution::search_range(nums, target), res);
}

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