Find First and Last Position of Element in Sorted Array Leetcode Solution

In this post, we are going to solve the Find First and Last Position of Element in Sorted Array Leetcode Solution problem of Leetcode. This Leetcode problem is done in many programming languages like C++, Java, and Python.

Table of Contents

Problem

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

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

You must 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

Now, let’s see the leetcode solution of Find First and Last Position of Element in Sorted Array Leetcode Solution.

Find First and Last Position of Element in Sorted Array Leetcode Solution in Python

class Solution:
  def searchRange(self, nums: List[int], target: int) -> List[int]:
    l = bisect_left(nums, target)
    if l == len(nums) or nums[l] != target:
      return -1, -1
    r = bisect_right(nums, target) - 1
    return l, r

Find First and Last Position of Element in Sorted Array Leetcode Solution in CPP

class Solution {
 public:
  vector<int> searchRange(vector<int>& nums, int target) {
    const int l = lower_bound(begin(nums), end(nums), target) - begin(nums);
    if (l == nums.size() || nums[l] != target)
      return {-1, -1};
    const int r = upper_bound(begin(nums), end(nums), target) - begin(nums) - 1;
    return {l, r};
  }
};

Find First and Last Position of Element in Sorted Array Leetcode Solution in Java

class Solution {
  public int[] searchRange(int[] nums, int target) {
    final int l = firstGreaterEqual(nums, target);
    if (l == nums.length || nums[l] != target)
      return new int[] {-1, -1};
    final int r = firstGreaterEqual(nums, target + 1) - 1;
    return new int[] {l, r};
  }

  // Finds the first index l s.t A[l] >= target
  // Returns A.length if can't find
  private int firstGreaterEqual(int[] A, int target) {
    int l = 0;
    int r = A.length;
    while (l < r) {
      final int m = (l + r) / 2;
      if (A[m] >= target)
        r = m;
      else
        l = m + 1;
    }
    return l;
  }
}

Note: This problem Find First and Last Position of Element in Sorted Array is generated by Leetcode but the solution is provided by Chase2learn This tutorial is only for Educational and Learning purposes.

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