Problem Explaination
In this blog, we discuss the solution to LeetCode Problem 3354: Make Array Elements Equal to Zero. Here's the problem statement:
You are given an integer array nums
. Starting at an index where nums[curr] == 0
, you can move in either the left or right direction. Follow these rules:
- If
nums[curr] == 0
, continue moving in the current direction. - If
nums[curr] > 0
, decrementnums[curr]
by 1, reverse your direction, and take a step. - Stop the process if
curr
goes out of bounds.
Your task is to find the number of valid (curr, direction)
pairs where the process ends with all elements of nums
reduced to zero.
Key Observations
Starting Points:
You can only start the process at indices wherenums[curr] == 0
.Directions:
For each valid starting position, both left and right directions need to be tested independently.Simulation:
The process can be simulated for each(curr, direction)
pair to verify if all elements ofnums
can be reduced to zero.Edge Cases:
- Arrays with no zeros (
nums
contains only non-zero values). - Arrays with all zeros (
nums
already satisfies the condition).
Approach:
To solve this problem, we:
- Identify all valid starting positions where
nums[curr] == 0
. - Simulate the process for both directions (
left
andright
) for each starting position. - Count the number of
(curr, direction)
pairs that lead to all elements ofnums
becoming zero.
Code:
Complexity Analysis:
Time Complexity:
- Simulating the process takes for each
(curr, direction)
. - Total complexity is , where is the length of the array.
- Simulating the process takes for each
Space Complexity:
- A copy of the array is created for simulation, so the space complexity is .
Conclusion:
This problem highlights the importance of simulation in solving array-based problems. By systematically analyzing valid starting positions and directions, we efficiently count all valid (curr, direction)
pairs. This approach ensures correctness and clarity.
https://dsablogtech.blogspot.com/2024/11/zero-array-transformation-i-leetcode.html
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