1702. Maximum Binary String After Change

Problem Link

Description

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You are given a binary string binary consisting of only 0's or 1's. You can apply each of the following operations any number of times:

• Operation 1: If the number contains the substring "00", you can replace it with "10".

  <ul>
  	<li>For example, <code>&quot;<u>00</u>010&quot; -&gt; &quot;<u>10</u>010</code>&quot;</li>
  </ul>
  </li>
  <li>Operation 2: If the number contains the substring <code>&quot;10&quot;</code>, you can replace it with <code>&quot;01&quot;</code>.
  <ul>
  	<li>For example, <code>&quot;000<u>10</u>&quot; -&gt; &quot;000<u>01</u>&quot;</code></li>
  </ul>
  </li>
  

Return the maximum binary string you can obtain after any number of operations. Binary string x is greater than binary string y if x's decimal representation is greater than y's decimal representation.

 

Example 1:

Input: binary = "000110"
Output: "111011"
Explanation: A valid transformation sequence can be:
"000110" -> "000101" 
"000101" -> "100101" 
"100101" -> "110101" 
"110101" -> "110011" 
"110011" -> "111011"

Example 2:

Input: binary = "01"
Output: "01"
Explanation: "01" cannot be transformed any further.

 

Constraints:

• 1 <= binary.length <= 105
• binary consist of '0' and '1'.

Solution

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Python3

class Solution:
    def maximumBinaryString(self, binary: str) -> str:
        if "0" not in binary: return binary
        
        idx = binary.index("0")
        
        res = []
        for _ in range(idx):
            res.append("1")
        
        ones = zeroes = 0
        for i in range(idx, len(binary)):
            if binary[i] == "1": ones += 1
            else: zeroes += 1
        
        while zeroes > 1:
            res.append("1")
            zeroes -= 1
        
        res.append("0")
        
        while ones > 0:
            res.append("1")
            ones -= 1
        
        return "".join(res)