[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