Is Time Needed to Rearrange a Binary String easy or hard?

The problem is rated Medium because the straightforward simulation is easy to code but inefficient. Recognizing the pattern that each '1' must pass preceding zeros—and translating that into a single-pass formula—requires stronger algorithmic insight.

How to solve Time Needed to Rearrange a Binary String in O(n)?

Traverse the string once while tracking the number of zeros seen so far. When encountering a '1' and there are preceding zeros, compute the time required using time = max(time + 1, zeros). This formula captures both the distance the '1' must travel and delays caused by earlier swaps, producing the answer in linear time.

Time Needed to Rearrange a Binary String Python or Java solution?

Python and Java implementations typically follow the same O(n) logic: iterate through the string, count zeros, and update a time variable using max(time + 1, zeros) whenever a '1' appears after zeros. The algorithm is short and requires only constant extra memory.

What is the best approach for Time Needed to Rearrange a Binary String?

The optimal approach scans the string once while counting how many zeros appear before each '1'. When a '1' appears after zeros, update the required time using time = max(time + 1, zeros). This analytical method avoids repeated simulation and runs in O(n) time with O(1) space.

Is Time Needed to Rearrange a Binary String asked at Google/Amazon/Meta?

Problems involving swap simulations, string transformations, and counting constraints frequently appear in interviews at companies like Amazon, Google, and Meta. Variations often test whether candidates recognize when a simulation can be converted into a linear analytical solution.

What data structure is used in Time Needed to Rearrange a Binary String?

The optimal solution does not require complex data structures. It uses simple counters while iterating through the string. The simulation version may treat the string as a mutable array or character list to swap adjacent elements.

What is the time complexity of Time Needed to Rearrange a Binary String?

The optimal analytical solution runs in O(n) time because it processes each character exactly once while maintaining counters for zeros and total time. A direct simulation approach can take O(n²) time in the worst case because the string may require up to n transformation rounds.

Description Hints 2 Solution Video 7:19

2380. Time Needed to Rearrange a Binary String

Medium53.3% acceptance5 companies

You are given a binary string s. In one second, all occurrences of "01" are simultaneously replaced with "10". This process repeats until no occurrences of "01" exist.

Return the number of seconds needed to complete this process.

Example 1:

Input: s = "0110101"
Output: 4
Explanation: 
After one second, s becomes "1011010".
After another second, s becomes "1101100".
After the third second, s becomes "1110100".
After the fourth second, s becomes "1111000".
No occurrence of "01" exists any longer, and the process needed 4 seconds to complete,
so we return 4.

Example 2:

Input: s = "11100"
Output: 0
Explanation:
No occurrence of "01" exists in s, and the processes needed 0 seconds to complete,
so we return 0.

Constraints:

1 <= s.length <= 1000
s[i] is either '0' or '1'.

Follow up:

Can you solve this problem in O(n) time complexity?

Asked at 5 companies

Salesforce PayPal Wayfair ServiceNow Amazon

Topics

Hints open one at a time

Hint 1

Try replicating the steps from the problem statement.

Hint 2

Perform the replacements simultaneously, and return the number of times the process repeats.

7:19

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