708479. Minimum times A has to be repeated such that B is a substring of it
Minimum times A has to be repeated such that B is a substring of it
Summary
Given two strings A and B, find the minimum number of times A should be repeated such that B becomes a substring of the repeated string. This problem involves pattern searching, strings, and algorithms.
Detailed Explanation
The key to solving this problem is to recognize that when B is a substring of the repeated string, it means that we have found a way to concatenate multiple copies of A such that B appears at some position in the resulting string. Therefore, our goal is to find the minimum number of times A should be repeated to achieve this.
Here's a step-by-step breakdown of the solution:
- Initialize a variable
countto 0. - Iterate through the length of
B. For each character inB, check if it exists in the current repetition ofA. - If the character is not found, increment
countand repeat step 2 until the character is found or we have iterated through the entire stringB. - The value of
countrepresents the minimum number of timesAshould be repeated such thatBbecomes a substring of it.
Here's an ASCII art diagram illustrating the process:
A : abcd
B : cd
Repeated A : abcdabcd
B is found in the second repetition!
Count = 2
Time complexity: O(|B| * |A|), where |B| and |A| are the lengths of strings B and A, respectively.
Space complexity: O(1), as we only need a few variables to store the count and indices.
Optimized Solutions
Java
public int minRepeatCount(String A, String B) {
int count = 0;
for (int i = 0; i < B.length(); i++) {
boolean found = false;
for (int j = 0; j <= count; j++) {
if (A.indexOf(B.charAt(i)) >= 0 && A.substring(j * A.length(), (j + 1) * A.length()).indexOf(B.charAt(i)) >= 0) {
found = true;
break;
}
}
if (!found) {
count++;
}
}
return count;
}