767. Reorganize String

Problem Link

Description

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Given a string s, rearrange the characters of s so that any two adjacent characters are not the same.

Return any possible rearrangement of s or return "" if not possible.

 

Example 1:

Input: s = "aab"
Output: "aba"

Example 2:

Input: s = "aaab"
Output: ""

 

Constraints:

• 1 <= s.length <= 500
• s consists of lowercase English letters.

Solution

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Python3

class Solution:
    def reorganizeString(self, s: str) -> str:
        counter = Counter(s)
        pq = []
        res = []
        
        for k, v in counter.items():
            heappush(pq, (-v, k))
        
        while pq:
            v, k = heappop(pq)
            v = -v
            
            if len(res) == 0 or res[-1] != k:
                res.append(k)
                if v - 1 > 0:
                    heappush(pq, (-(v - 1), k))
            else:
                if not pq: return ""
                v2, k2 = heappop(pq)
                v2 = -v2
                
                res.append(k2)
                if v2 - 1 > 0:
                    heappush(pq, (-(v2 - 1), k2))
                
                heappush(pq, (-v, k))
        
        return "".join(res)