FRK - Editorial

PROBLEM LINK:

Div2
Practice

Author: Misha Chorniy
Tester: Lewin Gan
Editorialist: Adarsh Kumar

DIFFICULTY:

Easy

PREREQUISITES:

Familiarity with strings.

PROBLEM:

You are given list of $N$ strings. You need to count number of strings in the given list, that have a common substring of length $\ge 2$ with the string "chef".

EXPLANATION:

For an input string and word "chef" to have a common substring of length $\ge 2$, input string must contain at-least one of the strings from following set as substring {"ch","he","ef","che","hef","chef"}. The set is redundant and can be reduced to {"ch","he","ef"} (Why?). Hence, you only need to check if two consecutive element from the input string is one from the above set. A pseudo-code to illustrate this:
def solve(N):
  ANS=0
  for i = 1...N:
    u = input*  # assume input* to be the ith string input
    l = len(u)   
    for j = 0...l-2:  # assume u to be in 0-based indexing
      if (u[j]=='c' && u[j+1]=='h')||(u[j]=='h' && u[j+1]=='e')||(u[j]=='e' && u[j+1]=='f'):
        ANS+=1
        break
  return ANS

Time Complexity:

$O(N.U)$, where $U$ = max length of input string.

AUTHOR'S AND TESTER'S SOLUTIONS

Setter's solution
Tester's solution