/*
 * @lc app=leetcode id=1138 lang=java
 *
 * [1138] Alphabet Board Path
 */

// @lc code=start
class Solution {
    public String alphabetBoardPath(String target) {
        char cur = 'a';
        StringBuilder bd = new StringBuilder();
        for(int i = 0; i < target.length(); i++) {
            bd.append(actions(cur, target.charAt(i)));
            cur = target.charAt(i);
        }
        return bd.toString();
    }

    private int[] distance(char a, char b) {
        int[] pa = new int[] {
            (a-'a') / 5,
            (a-'a') % 5
        };
        int[] pb = new int[] {
            (b - 'a') / 5,
            (b - 'a') % 5
        };
        return new int[] {
            pb[0] - pa[0],
            pb[1] - pa[1]
        };
    }

    private String actions(char s, char d) {
        int[] move = distance(s, d);
        StringBuilder builder = new StringBuilder();
        if(move[0] == 0 && move[1] == 0) {
            builder.append('!');
        } else {
            if(s == 'z') {
                builder.append(rowActions(move[0]));
                builder.append(colActions(move[1]));
            } else {
                builder.append(colActions(move[1]));
                builder.append(rowActions(move[0]));
            } 
            builder.append('!');
        }
        return builder.toString();
    }

    private String rowActions(int x) {
        if(x == 0) {
            return "";
        }
        return x > 0 ? repeatChar('D', x):repeatChar('U', -x);
    }

    private String colActions(int x) {
        if(x == 0) {
            return "";
        }
        return x > 0 ? repeatChar('R', x):repeatChar('L', -x);
    }

    private String repeatChar(char ch, int n) {
        StringBuilder s = new StringBuilder();
        for(int i = 0; i<n; i++) {
            s.append(ch);
        }
        return s.toString();
    }
}
// @lc code=end