704.Binary Search

tags: `Easy`,`Array`,`Binary Search`

題目描述

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.

範例

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.

解答

Javascript

















function search(nums, target) {
  let min = 0;
  let max = nums.length - 1;

  while (max >= min) {
    const mid = Math.floor((max + min) / 2);
    if (nums[mid] === target) return mid;
    
    if (nums[mid] > target) {
      max = mid - 1;
    } else {
      min = mid + 1;
    }
  }

  return -1;
}

MarsgoatApr 1, 2023

Python













class Solution:
    def search(self, nums: List[int], target: int) -> int:
        L, R = 0, len(nums)
        while L < R:
            M = (L + R) // 2
            n = nums[M]
            if n == target:
                return M
            if n > target:
                R = M
            else:
                L = M + 1
        return -1

Reference

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