 FRK - Editorial

Div2
Practice

Author: Misha Chorniy
Tester: Lewin Gan

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.