# Tag: python

## Python datetime strptime: unconverted data remains The datetime conversion function strptime() kept failing until the invisible error got caught!

## K-Messed Array Sort: Python Solution

K-Messed Array Sort Given an array of integers arr where each element is at most k places away from its sorted position Solution from Queue import PriorityQueue def sort_k_messed_array(arr, k): kheap = PriorityQueue() result = [] for num in arr: kheap.put(num, ‘num’) if kheap.qsize() == (k + 1): item = kheap.get() result.append(item) while not kheap.empty():…

## Python Coding Tips: Set & List

The following code snippets are very helpful during sets and list operations. Intersection of sets must check for valid case \$ cat sets.py s1 = {1,2,3} s2 = {} # empty sets means the intersection is empty too! s3 = {} if set(s1) & set(s2): print(s1.intersection(s2)) else: print(“no intersection”) Result \$ python sets.py no intersection…

## Python Collections: Counter

Many times we need to keep track of frequencies of unique keys. We can always use a dictionary but counter is more appropriate for its brevity. Python collections define the counter class. Counter works on any iterator and generates a count of elements. So it has a natural use case on the list 🙂 from…

## Find Number with More Than 25 Percent Frequency In Sorted Array

Leetcode Element Appearing More Than 25% In Sorted Array class Solution(object): def findSpecialInteger(self, arr): “”” :type arr: List[int] :rtype: int “”” if len(arr) > 8: return self.getMostFrequentNumberOptimized(arr) return self.getMostFrequentNumber(arr) def getMostFrequentNumber(self, arr): counter = {} for n in arr: if n in counter: counter[n] += 1 else: counter[n] = 1 targetPercent = (len(arr) * 25)//100…

## K Weakest Rows in a Matrix

Problem The K Weakest Rows in a Matrix Solution Uses Binary search to count 1s Uses heap to keep k weakest rows It naturally satisfies the condition for weak rows with the same number of soldiers. The smaller index row is processed first and hence any next row would not get pushed to the heap.…

## Number of 1s in a sorted array

Problem Count number of 1s in a sorted array. e.g. [1,1,1,1,0,0,0,0,0,0] Code def countOneBS(row, start, end): if row[start] == 0: return 0 if row[end] == 1: return end – start + 1 # The mid is dependent on the index of start mid = start + (end – start) // 2 # print(“mid=”, mid, “start=”,…

## Why Use Python Ordered Dictionary?

An ordered dictionary offers same time complexity as the standard dict. The implementation is simple: Keep two dictionaries and a doubly-linked list of keys. The DLL maintains order. One dict maps key => DLL node Other dict maps key => value Implementation details https://github.com/python/cpython/blob/3.7/Lib/collections/init.py#L129 Example Problem: Find the first non-repeating char in a string. def…

## Another Solution: Longest Palindrome Substring

class Solution(object): def __init__(self): self.lookup = {“test”} def isPalindrome(self, s, i, k): j = i + k – 1 if s[i] == s[j]: key = self.createKey(i + 1, j – 1) if key in self.lookup: #self.lookup.remove(key) return True return False def createKey(self, i, j): #return “{}:{}”.format(i,j) #return (i, j) #key = bin(i) + bin(j) #return…