Quick Overview

This collection evaluates proficiency in fundamental data structures and algorithms — including tree traversal and binary search tree reasoning, array manipulation and counting, string/stack validation for parentheses, prefix-sum range queries, and basic dynamic programming — within the Coding & Algorithms domain.

Solve various LeetCode data-structure questions

Company: Meta

Role: Software Engineer

Category: Coding & Algorithms

Difficulty: medium

Interview Round: Onsite

##### Question LeetCode 129. Sum Root to Leaf Numbers LeetCode 2089. Find Target Indices After Sorting Array LeetCode 270. Closest Binary Search Tree Value LeetCode 1249. Minimum Remove to Make Valid Parentheses LeetCode 303. Range Sum Query – Immutable LeetCode 746. Min Cost Climbing Stairs https://leetcode.com/problems/sum-root-to-leaf-numbers/description/ https://leetcode.com/problems/find-target-indices-after-sorting-array/description/ https://leetcode.com/problems/closest-binary-search-tree-value/description/ https://leetcode.com/problems/minimum-remove-to-make-valid-parentheses/description/ https://leetcode.com/problems/range-sum-query-immutable/description/ https://leetcode.com/problems/min-cost-climbing-stairs/description/

Overview: This collection evaluates proficiency in fundamental data structures and algorithms — including tree traversal and binary search tree reasoning, array manipulation and counting, string/stack validation for parentheses, prefix-sum range queries, and basic dynamic programming — within the Coding & Algorithms domain.

Given an integer array nums and an integer target, sort nums in non-decreasing order and return a list of all indices where target appears in the sorted array. Indices are 0-based and must be returned in increasing order.

Constraints

  • 1 <= len(nums) <= 100000
  • -10^9 <= nums[i] <= 10^9
  • -10^9 <= target <= 10^9
  • Return indices in increasing order

Hints

  1. Sorting nums and scanning for target works in O(n log n).
  2. You can avoid sorting: count how many elements are less than target and how many equal target.
  3. If cLess is the count of elements < target and cEq is the count == target, the answer is the range [cLess, cLess + cEq - 1].

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Show the approach

Approach

Instead of sorting, count how many elements are less than target (less) and how many are equal to target (equal). In the sorted array, all elements less than target come first, so target will start at index 'less' and occupy 'equal' consecutive positions. Construct and return that index range. If the target does not appear, return an empty list.

Time complexity:
O(n)
Space complexity:
O(1) auxiliary (excluding output)