LeetCode 2851: String Transformation Solution

Master LeetCode problem 2851 (String Transformation), 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.

2851. String Transformation

Hard

Math String Dynamic Programming String Matching

Problem Explanation

Explanation

To solve this problem, we can iterate over all possible suffix lengths l from 1 to n-1 and check if we can transform string s into string t in k operations by removing a suffix of length l and appending it at the start. We can keep track of the number of ways we can transform s into t in exactly k operations.

Algorithm

Initialize a count variable to keep track of the number of ways to transform s into t in k operations.
Iterate over all possible suffix lengths l from 1 to n-1.
For each suffix length l, check if transforming s into t in exactly k operations is possible.
If it is possible, increment the count.
Return the count modulo 10^9 + 7.

Time Complexity

The time complexity of this algorithm is O(n) where n is the length of the input strings s and t.

Space Complexity

The space complexity of this algorithm is O(1) as we are using only a constant amount of extra space.

Solution Code

class Solution {
    public int numTransforms(String s, String t, int k) {
        int n = s.length();
        int count = 0;
        long MOD = 1000000007;

        for (int l = 1; l < n; l++) {
            if ((long) (n - l) * k + l >= n && checkTransform(s, t, l)) {
                count++;
            }
        }

        return count % MOD;
    }

    private boolean checkTransform(String s, String t, int l) {
        String suffix = s.substring(s.length() - l); // Remove suffix
        String newS = suffix + s.substring(0, s.length() - l); // Append suffix at the start
        return newS.equals(t);
    }
}

Try It Yourself

Loading code editor...

Frequently Asked Questions

How to solve LeetCode 2851 (String Transformation)?

This page provides optimized solutions for LeetCode problem 2851 (String Transformation) in Java, C++, and Python, along with a detailed explanation and an interactive code editor to test your code.

What is the time complexity of LeetCode 2851 (String Transformation)?

The time complexity for LeetCode 2851 (String Transformation) varies by solution. Check the detailed explanation section for specific complexities in Java, C++, and Python implementations.

Can I run code for LeetCode 2851 on DevExCode?

Yes, DevExCode provides an interactive code editor where you can write, test, and run your code for LeetCode 2851 in Java, C++, or Python.

Back to LeetCode Solutions