LeetCode 1138: Alphabet Board Path Solution

Master LeetCode problem 1138 (Alphabet Board Path), a medium 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.

1138. Alphabet Board Path

Medium

Hash Table String

Problem Explanation

Explanation

To solve this problem, we can iterate over the characters in the target string and calculate the moves required to move from one character to the next on the alphabet board. We can use a helper function to generate the path for each character using the shortest path possible.

We need to consider special cases when moving to or from the letter 'z' because it is positioned differently on the board compared to other letters.

The algorithm involves calculating the row and column differences between the current position and the target character position and determining the shortest path to move accordingly. We also need to account for the special case of 'z' and handle it separately.

The time complexity of this algorithm is O(n), where n is the length of the target string. The space complexity is also O(n) to store the result of the moves.

Solution Code

class Solution {
    public String alphabetBoardPath(String target) {
        StringBuilder sb = new StringBuilder();
        int row = 0, col = 0;

        for (char c : target.toCharArray()) {
            int tr = (c - 'a') / 5;
            int tc = (c - 'a') % 5;

            while (row > tr) {
                sb.append('U');
                row--;
            }

            while (col < tc) {
                sb.append('R');
                col++;
            }

            while (col > tc) {
                sb.append('L');
                col--;
            }

            while (row < tr) {
                sb.append('D');
                row++;
            }

            sb.append('!');
        }
        
        return sb.toString();
    }
}

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