2938. Separate Black and White Balls LeetCode Solution

In this guide, you will get 2938. Separate Black and White Balls LeetCode Solution with the best time and space complexity. The solution to Separate Black and White Balls problem is provided in various programming languages like C++, Java, and Python. This will be helpful for you if you are preparing for placements, hackathons, interviews, or practice purposes. The solutions provided here are very easy to follow and include detailed explanations.

Table of Contents

  1. Problem Statement
  2. Complexity Analysis
  3. Separate Black and White Balls solution in C++
  4. Separate Black and White Balls solution in Java
  5. Separate Black and White Balls solution in Python
  6. Additional Resources
2938. Separate Black and White Balls LeetCode Solution image

Problem Statement of Separate Black and White Balls

There are n balls on a table, each ball has a color black or white.
You are given a 0-indexed binary string s of length n, where 1 and 0 represent black and white balls, respectively.
In each step, you can choose two adjacent balls and swap them.
Return the minimum number of steps to group all the black balls to the right and all the white balls to the left.

Example 1:

Input: s = “101”
Output: 1
Explanation: We can group all the black balls to the right in the following way:
– Swap s[0] and s[1], s = “011”.
Initially, 1s are not grouped together, requiring at least 1 step to group them to the right.
Example 2:

Input: s = “100”
Output: 2
Explanation: We can group all the black balls to the right in the following way:
– Swap s[0] and s[1], s = “010”.
– Swap s[1] and s[2], s = “001”.
It can be proven that the minimum number of steps needed is 2.

See also  1719. Number Of Ways To Reconstruct A Tree LeetCode Solution

Example 3:

Input: s = “0111”
Output: 0
Explanation: All the black balls are already grouped to the right.

Constraints:

1 <= n == s.length <= 105
s[i] is either '0' or '1'.

Complexity Analysis

  • Time Complexity: O(n)
  • Space Complexity: O(1)

2938. Separate Black and White Balls LeetCode Solution in C++

class Solution {
 public:
  long long minimumSteps(string s) {
    long ans = 0;
    int ones = 0;

    for (const char c : s)
      if (c == '1')
        ++ones;
      else  // Move 1s to the front of the current '0'.
        ans += ones;

    return ans;
  }
};
/* code provided by PROGIEZ */

2938. Separate Black and White Balls LeetCode Solution in Java

class Solution {
  public long minimumSteps(String s) {
    long ans = 0;
    int ones = 0;

    for (final char c : s.toCharArray())
      if (c == '1')
        ++ones;
      else // Move 1s to the front of the current '0'.
        ans += ones;

    return ans;
  }
}
// code provided by PROGIEZ

2938. Separate Black and White Balls LeetCode Solution in Python

class Solution:
  def minimumSteps(self, s: str) -> int:
    ans = 0
    ones = 0

    for c in s:
      if c == '1':
        ones += 1
      else:  # Move 1s to the front of the current '0'.
        ans += ones

    return ans
# code by PROGIEZ

Additional Resources

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