LeetCode 3031: Minimum Time to Revert Word to Initial State II Solution
Master LeetCode problem 3031 (Minimum Time to Revert Word to Initial State II), a hard challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.
3031. Minimum Time to Revert Word to Initial State II
Problem Explanation
Explanation
To solve this problem, we need to simulate the process of removing the first k characters and adding any k characters to the end of the word at each second until the word reverts to its initial state. We will keep track of the current state of the word at each step and check if it matches the initial word state.
We can optimize the process by observing that if the word does revert to its initial state, it must be a rotation of the initial word. Therefore, we can concatenate the initial word with itself and find the longest prefix that is a suffix in this concatenated word. This will give us the length of the shortest rotation that reverts the word to its initial state.
The time complexity of this approach is O(n), where n is the length of the word, and the space complexity is O(n) to store the concatenated word.
Solution Code
class Solution {
public int minTimeToType(String word, int k) {
String initialWord = word;
word += word;
int n = word.length();
int[] lps = new int[n];
// Calculate the longest prefix that is also a suffix
int len = 0, i = 1;
while (i < n) {
if (word.charAt(i) == word.charAt(len)) {
len++;
lps[i] = len;
i++;
} else {
if (len != 0) {
len = lps[len - 1];
} else {
lps[i] = 0;
i++;
}
}
}
int repeatLength = n - lps[n - 1];
return repeatLength / initialWord.length();
}
}Try It Yourself
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