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Ninja and Numbers
MEDIUM
25 mins
4 upvotes
Strings
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Ninja and Numbers

Contributed by
Smit Mistry
Medium
yellow-spark
0/80
Avg time to solve 25 mins
Success Rate 75 %
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4 upvotes

Problem Statement

Ninja has a number ‘A’ containing ‘B’ digits. ‘A’ can be represented by a string ‘S’ where ‘S[i]’ denotes the ‘ith’ digit of ‘A’. You are also given an integer ‘K’.

Ninja thinks that a number is stable if the following condition is satisfied:

For every ‘ith’ digit where (0 <= ‘i’ <= ‘B-1’) ‘S[i] = S[i%K]’. Here, ‘X%Y’ represents the modulo operations. The remainder when ‘X’ is divided by ‘Y’.

Your task is to find the smallest number which is stable and whose value is greater than or equal to ‘A’. Zero-based indexing is used everywhere.

Example :
‘B’ = 4, ‘S’ = “4321”, ‘K’ = 3.
The given number is not stable as ‘S[3]’ is not the same as ‘S[0]’ but 3%3 = 0 same as 0%3. ‘S[3] = 1’ and ‘S[0] = 4’.  But the number “4324” is stable. As, for all ‘i’, ‘S[i]’ = ‘S[i%K]’ and “4324” is also greater than the given number. It can be proved that this is the best possible answer.
Hence, the answer is “4324”.
Detailed explanation ( Input/output format, Notes, Constraints, Images )
Sample Input 1 :
2
4 2
6825
3 3
420
Sample Output 1 :
6868
420
Explanation For Sample Input 1 :
For test case 1: 
6868 is the minimum possible, stable number. We can see that it is stable because ‘S[0] = S[2]’ because 0%2 = 2%2, and ‘S[1] = S[3]’ because 1%2 = 3%2. All the conditions are satisfied.
Hence, 6868 is the answer.

For test case 2:
The given number itself is stable, and hence it is the best possible answer.
Sample Input 2 :
2
5 1
40369
4 2
8516
Sample Output 2 :
44444
8585
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