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Python: Check if the letters of a given string can be rearranged so that two characters that are adjacent to each other are different

Python heap queue algorithm: Exercise-15 with Solution

Write a Python program to check if the letters of a given string can be rearranged so that two characters that are adjacent to each other are different using Heap queue algorithm.

Note:
If there is no output return the empty string.

Sample Solution:

Python Code:

import heapq
from collections import Counter
def reorganizeString(S):
    ctr = Counter(S)
    heap = [(-value, key) for key, value in ctr.items()]
    heapq.heapify(heap)
    if (-heap[0][0]) * 2 > len(S) + 1: 
        return ""
    ans = []
    while len(heap) >= 2:
        nct1, char1 = heapq.heappop(heap)
        nct2, char2 = heapq.heappop(heap)
        ans.extend([char1, char2])
        if nct1 + 1: heapq.heappush(heap, (nct1 + 1, char1))
        if nct2 + 1: heapq.heappush(heap, (nct2 + 1, char2))
    return "".join(ans) + (heap[0][1] if heap else "")

print(reorganizeString("aab"))
print(reorganizeString("abc"))
print(reorganizeString("aabb"))
print(reorganizeString("abccdd"))

Sample Output:

aba
abc
abab
cdabcd

Flowchart:

Python heap queue algorithm: Check if the letters of a given string can be rearranged so that two characters that are adjacent to each other are different.

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Python Code Editor:

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Previous: Write a Python program to get the k most frequent elements from a given non-empty list of words using Heap queue algorithm.
Next: Write a Python program which add integer numbers from the data stream to a heapq and compute the median of all elements.

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Python: Tips of the Day

Creates a dictionary with the same keys as the provided dictionary and values generated by running the provided function for each value:

Example:

def tips_map_values(obj, fn):
  ret = {}
  for key in obj.keys():
    ret[key] = fn(obj[key])
  return ret
users = {
  'Owen': { 'user': 'Owen', 'age': 29 },
  'Eddie': { 'user': 'Eddie', 'age': 15 }
}

print(tips_map_values(users, lambda u : u['age'])) # {'Owen': 29, 'Eddie': 15}

Output:

{'Owen': 29, 'Eddie': 15}