[Graph] - DAG : An important observation

In a DAG, a mutually unreachable pair (s,t) can exist if and only if there exists at least one topological level with at least two nodes. 

Read the post at Notion : https://www.notion.so/DAG-Directed-Acyclic-Graph-1d8d32fa6ba880e7aea2d3eb59ad46e1

Leetcode Weekly Contest 441 Q2. Closest Equal Element Queries

Q2. Closest Equal Element Queries

⭐Important learnings wrt 🔁Circular Array🔁  : 

 The two distances between elt at i & j  : 

• forward_dist  = (j-i+n) % n;
• backward_dist = (i-j+n) % n; 

How to get the two indexes `d` distance away from a given index, i ?

• next_d_idx = ( i + d) % n ;
• prev_d_idx = ( i - d + n) % n ;

As a special case when d=1, we can get next & prev elements as : 

• next_idx = (i+1) % n 
• prev_idx = (i-1+n ) % n

Alternatively, the +1 for forward should be thought as +(n-1) for backward or more generally, +d should be thought as +(n-d) when marching in backward direction.

"Mastering Power Set Generation: A Deep Dive into Recursion” from a Java ☕ programmer’s perspective

Motivation for the notes :

1. Leetcode#78. Subsets 
2. G4G Power Set 

There are broadly two approaches :

1. Bit Masking (iterative) 😷{not focus of this blog}
2. Backtracking (recursive) ⭐
   1. Include-Exclude paradigm : here we see two variants & why we should use one over other
   2. For-loop paradigm : prefer this (reason at the end)

Continue reading my latest blog compiled at notion.so by clicking here :  "Mastering Power Set Generation: A Deep Dive into Recursion” from a Java ☕ programmer’s perspective

SUNY Buffalo : MS Tracks and Specializations (Graphic Representation)

Graduate degree options provided by Departement of CSE at SUNY Buffalo can be graphically represented as : 

 

(Click on the images for enlarged view 🔍)

The graphic representation of the semester wise breakdown of programm can be depicted as : 

Please comment below if you find anything wrong in the representations. Or, if you want to add more in this.

LineRandomizer in Python : Utility Function

While Memorizing vocab for GRE, I decided to jumble up my word list in random order. This small python utility program helped me achieve that. Hope it helps you as well. 

'''

Author: Kunal Krishna

Date: 30/05/2023

'''

'''

Programme Purpose : Given a text file containing N lines,

    return a new file which has reorder those lines in random order.

    This has many utilities e.g. in memorizing a list of vocabulary.

Input: File1.text :

    >a

    >b

    >c

Output: File2.text : Random ordering

    >c

    >a

    >b

'''

import os

import re

import random

import numpy as np

# 1. Open file.txt : https://docs.python.org/3/library/functions.html#open

inpFile= open("D:\[win.kunal]\Desktop\Diff_Words.txt","r")

linesList = inpFile.readlines() #list of lines

# for line in linesList :

#     line = line.strip("\n")

# 2. Create an output file

resPath= "D:\my_codes\py_code\LineRandomizer"

resFileName = 'Difficult_Words.txt'

file_result = open(os.path.join(resPath,resFileName), "w") # w : creates/overrides existing

# alternatively

# file_result = open("Difficult_Words.txt", "w")

count = 0

# 3.Process the lines : randomize

while (len(linesList) > 0) :

    #chose a random word from the list

    random_word = np.random.choice(linesList)

    validWordExpression = "[~\*\#\w\s]"

    if( len(random_word.strip()) >0

            and re.match(validWordExpression, random_word) ) :

        # write the random word in the new file

        print(str(count+1)+". inserting..." + random_word.upper())

        file_result.write(random_word.upper())

        count +=1

    #also remove the word from linesList to avoid repetation

    linesList.remove(random_word)

# 4. Close the file

inpFile.close()

file_result.close()

if count>0 :  

    print(str(count)+" words inserted successfully!!!")

else :  

    print("No word(s) inserted.")