LUCKYN - Editorial

editorial
,
1

PROBLEM LINK:

Practice
Contest: Division 1
Contest: Division 2
Contest: Division 3
Contest: Division 4

Author: jeevanjyot
Testers: mexomerf, rivalq
Editorialist: iceknight1093

DIFFICULTY:

TBD

PREREQUISITES:

None

PROBLEM:

An integer is said to be lucky if it contains the digit 7.
Given a positive integer X, is it lucky?

EXPLANATION:

All that needs to be done is to check, for each digit of X, whether it equals 7.

Extracting all the digits of an integer can be done in a couple of different ways:

  • The simplest way is to read X as a string instead of an integer. Then, you can simply iterate over its characters and check whether each one equals '7' or not.
  • Alternately, run the following algorithm:
    • If X = 0, stop.
    • Otherwise, let d = X%10. d is the last digit of X, check whether it equals 7 or not.
    • Next, divide X by 10. This essentially removes the last digit of X.
    • Run the above three steps in a loop; hence extracting every digit of X.

TIME COMPLEXITY:

\mathcal{O}(1) per testcase.

CODE:

Code (Python) (String) 
for _ in range(int(input())):
    x = input()
    print('Yes' if '7' in x else 'No')
Code (Python) (Loop) 
for _ in range(int(input())):
    x = int(input())
    ans = 'No'
    while x > 0:
        d = x%10
        if d == 7: ans = 'Yes'
        x //= 10
    print(ans)