Binary search

Array Binary Search

60.5% acceptance

Feb 21, 2026

13378

300

Given an array of integers nums which is sorted in ascending order, and an integer target, write a function to search target in nums. If target exists, then return its index. Otherwise, return -1. You must write an algorithm with O(log n) runtime complexity.

Solution

Rust

Time O(n log n)

Space O(1)

LeetCode

solution.rs

/*
 * Given an array of integers nums which is sorted in ascending order, and an integer target, write a function to search target in nums. If target exists, then return its index. Otherwise, return -1.
 * You must write an algorithm with O(log n) runtime complexity.
 * Example 1:
 * Input: nums = [-1,0,3,5,9,12], target = 9
 * Output: 4
 * Explanation: 9 exists in nums and its index is 4
 * Example 2:
 * Input: nums = [-1,0,3,5,9,12], target = 2
 * Output: -1
 * Explanation: 2 does not exist in nums so return -1
 * Constraints:
 * 1 <= nums.length <= 104
 * -104 < nums[i], target < 104
 * All the integers in nums are unique.
 * nums is sorted in ascending order.
 */
impl Solution {
  pub fn search(nums: Vec<i32>, target: i32) -> i32 {
    let (mut lo, mut hi) = (0i32, nums.len() as i32 - 1);
    while lo <= hi {
      let mid = lo + (hi - lo) / 2;
      match nums[mid as usize].cmp(&target) {
        std::cmp::Ordering::Equal => return mid,
        std::cmp::Ordering::Less => lo = mid + 1,
        std::cmp::Ordering::Greater => hi = mid - 1,
      }
    }
    -1
  }
}