003_reverse_array_queries

Reverse Array Queries

• 🧩 Problem link: Amazon HackerRank Demo OA practice test
• 🚦 Difficulty: 🟡 Medium

💡 Approach

• The function applies a sequence of reverse operations on an array.

• For each operation [left, right]:

  • Reverse the subarray between indices left and right (inclusive).
  • This is done with a two-pointer swap until left >= right.

• After applying all operations, return the final modified array.

🕒 Time and Space Complexity

• Time: O(m * n)
• Space: O(1)

Where n is operations.size() and m is arr.size()

✅ Solution

vector<int> performOperations(vector<int> arr, vector<vector<int>> operations)
{
    for (vector<int> curOp : operations) // O(n)
    {
        int left = curOp[0], right = curOp[1];

        while (left < right) // O(m)
        {
            int temp = arr[left];
            arr[left] = arr[right];
            arr[right] = temp;
            left++;
            right--;
        }
    }

    return arr;
};